We can add a ChildViewController using container by following code.

-(void)addChildViewController{
    UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    NSString *strClass = NSStringFromClass([YourChildViewController class]);
    YourChildViewController *vc = [sb instantiateViewControllerWithIdentifier:strClass];
    if (self.childViewControllers.count > 0 ) //check if container already has any ChildViewcontroller
    {
     // replace it with another child controller.
        [self swapFromViewController:[self.childViewControllers objectAtIndex:0] toViewController:vc];
    }
    else
    {
       // else add ChildViewController to container.
       [self addChildControllerForFirstTime:vc];
    }
}

// To swap child controller 
 - (void)swapFromViewController:(UIViewController *)fromViewController toViewController:(UIViewController *)toViewController
 {
    toViewController.view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
    [fromViewController willMoveToParentViewController:nil];
    [self addChildViewController:toViewController];
    [self transitionFromViewController:fromViewController toViewController:toViewController duration:0.2 options:UIViewAnimationOptionTransitionCrossDissolve animations:nil completion:^(BOOL finished) {
        [fromViewController removeFromParentViewController];
        [toViewController didMoveToParentViewController:self];
    }];
 }

//To add child controller 
- (void)addChildControllerForFirstTime:(UIViewController*)vc{
    [self addChildViewController:vc];
    ((UIViewController *)vc).view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
    [self.view addSubview:((UIViewController *)vc).view];
    [vc didMoveToParentViewController:self];
}