In order to use the auth component. You have to add the component to the AppController. (/app/Controller/AppController.php)

var $components = array('Auth');

Define $components array in your controller.

public $components = array(
   'Auth' => array(
     'authenticate' => array(
       'Form' => array (
          'fields' => array('username'=>'email','password'=>'user_password')
        )
     )
   )
);

You can assign loginredirect and logoutredirect as well as other parameters in beforefilter function in your controller.

function beforFilter()
{
  // Display action to be accessed without user login is allowed.
  $this->Auth->allow('display');

  //loginRedirect defines the action called after user logged in first-time.
  $this->Auth->loginRedirect = array('controller'=>'users','action'=>'dashboard');

  //loginRedirect tell the component where to redirect to user after log-out.
  $this->Auth->logoutRedirect = array('controller'=>'users','action'=>'login');
}

Now Define login and logout methods in the UsersController file

function login ()
{
  //Check user credentials and redirect to user based on that.
  if($this->Auth->login())
  {
    //It automatically redirect to loggedin url which we set earlier above in beforerfilter.
  } 
  else
  {
    //Print a Messege that username or password is wrong if authenticate fails.
    $this->Session->setFlash('Invalid Username or Password,try again');
  }
}

function logout()
{
  $this->redirect($this->Auth->logout());
}

So by using above flow of code you will successfully use auth component in cakephp.