Hi,

Download Facebook SDK from following link- https://developers.facebook.com/docs/ios

Add SDK to your project. This code will help you login and get user data as well fetch friend list from specific account.

FBManager - Create a file and write the following content in FBManager.h

#import <Foundation/Foundation.h>
#import <FacebookSDK/FacebookSDK.h>

@interface MyFBManager : NSObject{

    void (^completionBlock)(id data, BOOL success);

}


+ (MyFBManager *)sharedManager;

- (void)loginToFB:(void(^)(id data, BOOL result))block;

- (void)getUserBasicData:(void(^)(id userValue, BOOL result))block;

- (void)getMyFBFriends:(void(^)(id friends, BOOL result))block;

- (void)getMyFBPictures:(void(^)(id data, BOOL result))block;

- (BOOL)isAlreadyLoggedIn;

- (void)logoutFromFB:(void(^)(id data, BOOL result))block;

@end

FBManager.m

#import "MyFBManager.h"


@implementation MyFBManager

static MyFBManager *myFBManager =  nil;

+ (MyFBManager *)sharedManager{

    if (!myFBManager) {

        myFBManager = [[MyFBManager alloc]init];
    }

    return myFBManager;
}


- (BOOL)isAlreadyLoggedIn{

    return [FBSession activeSession].accessTokenData.accessToken.length?YES:NO;
}

- (void)loginToFB:(void(^)(id data, BOOL result))block{

    NSLog(@"Login in to FB");

    if ([[FBSession activeSession] isOpen]) {

        NSLog(@"session is active");

        block([FBSession activeSession].accessTokenData.accessToken, YES);
    }
    else{

        [FBSession openActiveSessionWithReadPermissions:[NSArray arrayWithObjects:@"email",@"user_location",@"user_groups", nil]  allowLoginUI:YES completionHandler:^(FBSession *session, FBSessionState status, NSError *error) {



            if (error) {
                NSLog(@"errror==%ld==%@",(long)error.code,error.debugDescription);
                UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error"
                                                                message:error.localizedDescription
                                                               delegate:nil
                                                      cancelButtonTitle:@"OK"
                                                      otherButtonTitles:nil];
                [alert show];
                // if otherwise we check to see if the session is open, an alternative to
                // to the FB_ISSESSIONOPENWITHSTATE helper-macro would be to check the isOpen
                // property of the session object; the macros are useful, however, for more
                // detailed state checking for FBSession objects

                block(nil, YES);

            } else if (FB_ISSESSIONOPENWITHSTATE(status)) {
                // send our requests if we successfully logged in
                //                                              [self sendRequests];



                NSLog(@"access token is== %@", session.accessTokenData.accessToken);

                block(session.accessTokenData.accessToken, YES);

            }

        }];
    }


}




- (void)sessionStateChanged:(FBSession *)session state:(FBSessionState) state error:(NSError *)error
{
    // If the session was opened successfully
    if (!error && state == FBSessionStateOpen){
        NSLog(@"Session opened");

//        [self getUserBasicData];
        return;
    }
    if (state == FBSessionStateClosed || state == FBSessionStateClosedLoginFailed){
        // If the session is closed
        NSLog(@"Session closed");
        // Show the user the logged-out UI
        //        [self userLoggedOut];
    }

    // Handle errors
    if (error){
        NSLog(@"Error");
        NSString *alertText;
        NSString *alertTitle;
        // If the error requires people using an app to make an action outside of the app in order to recover
        if ([FBErrorUtility shouldNotifyUserForError:error] == YES){
            alertTitle = @"Something went wrong";
            alertText = [FBErrorUtility userMessageForError:error];

            //            [self showMessage:alertText withTitle:alertTitle];

        } else {

            // If the user cancelled login, do nothing
            if ([FBErrorUtility errorCategoryForError:error] == FBErrorCategoryUserCancelled) {
                NSLog(@"User cancelled login");

                // Handle session closures that happen outside of the app
            } else if ([FBErrorUtility errorCategoryForError:error] == FBErrorCategoryAuthenticationReopenSession){
                alertTitle = @"Session Error";
                alertText = @"Your current session is no longer valid. Please log in again.";
                //                [self showMessage:alertText withTitle:alertTitle];

                // For simplicity, here we just show a generic message for all other errors
                // You can learn how to handle other errors using our guide: https://developers.facebook.com/docs/ios/errors
            } else {
                //Get more error information from the error
                //                NSDictionary *errorInformation = [[[error.userInfo objectForKey:@"com.facebook.sdk:ParsedJSONResponseKey"] objectForKey:@"body"] objectForKey:@"error"];

                // Show the user an error message
            }
        }
        // Clear this token
        [FBSession.activeSession closeAndClearTokenInformation];
        // Show the user the logged-out UI
        //        [self userLoggedOut];
    }
}

-(void)getUserBasicData:(void(^)(id userValue, BOOL result))block
{

    NSLog(@"getting details here");

    if (![[FBSession activeSession] isOpen]){

        [[[UIAlertView alloc]initWithTitle:@"Please Login" message:@"Login to FB first" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil] show];
        block(nil, NO);
        return;
    }

    [FBRequestConnection startForMeWithCompletionHandler:^(FBRequestConnection *connection, id result, NSError *error)
     {
         block(result, error?NO:YES);
     }];

}


- (void)getMyFBFriends:(void(^)(id friends, BOOL result))block{

    [FBRequestConnection startForMyFriendsWithCompletionHandler:^(FBRequestConnection *connection, id result, NSError *error) {


        block(result, error?NO:YES);

    }];
}


- (void)uploadTheImageToFB:(UIImage *)image withTitle:(NSString *)title description:(NSString *)description completionBlock:(void(^)(id responseData, BOOL result))block{


    //  Uploading image to user's photos on Facebook
    NSMutableDictionary * params = [NSMutableDictionary dictionaryWithObjectsAndKeys:[FBSession activeSession].accessTokenData.accessToken,@"access_token",description, @"message",nil];
    if (image) {
        [params setObject:image forKey:@"source"];
    }

    [FBSession setActiveSession:[FBSession activeSession]];

    [FBRequestConnection startWithGraphPath:@"me/photos"
                                 parameters:params HTTPMethod:@"POST"
                          completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {

                              block(result, error?NO:YES);

                          }];

}


- (void)getMyFBPictures:(void(^)(id data, BOOL result))block{

    [FBRequestConnection startWithGraphPath:@"/me/photos"
                                 parameters:nil
                                 HTTPMethod:@"GET"
                          completionHandler:^(
                                              FBRequestConnection *connection,
                                              id result,
                                              NSError *error
                                              ) {

                              block(result, error?NO:YES);

                          }];
}




-(void)getMyFBGroups:(void (^)(id, BOOL))block
{
    if (![[FBSession activeSession] isOpen]){

        [[[UIAlertView alloc]initWithTitle:@"Please Login" message:@"Login to FB first" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil] show];

        block(nil, NO);
        return;

    }



    [FBRequestConnection startWithGraphPath:@"/me/groups"
                                 parameters:nil
                                 HTTPMethod:@"GET"
                          completionHandler:^(
                                              FBRequestConnection *connection,
                                              id result,
                                              NSError *error
                                              ) {
                              NSLog(@"result %@",result);

                              block(result,error?NO:YES);
                          }];


}

-(void)getFacebookGroupDetail:(NSString *)groupId completionBlock:(void(^)(id responseData, BOOL result))block
{
    NSString *str=[NSString stringWithFormat:@"/%@/members",groupId];
    [FBRequestConnection startWithGraphPath:str
                                 parameters:nil
                                 HTTPMethod:@"GET"
                          completionHandler:^(
                                              FBRequestConnection *connection,
                                              id result,
                                              NSError *error
                                              ) {

                              block(result,error?NO:YES);
                              /* handle the result */
                          }];
}




- (void)logoutFromFB:(void(^)(id data, BOOL result))block{

    [FBSession.activeSession closeAndClearTokenInformation];

    block(Nil, YES);
}

Thanks.