How to trigger LaunchScreen storyboard from Login(authentication storyboard)

Hi, I now have two storyboard one for login/register, and the other one for the launching home page.

The second one I had a side navigation bar(follow the step from Xamarin component, so the LaunchScreen has it's own rootviewcontroller).

Then from the AppDelegate.cs : I had following:

public LaunchViewController RootViewController { get { return Window.RootViewController as LaunchViewController; } }

 public override bool LaunchViewController(UIApplication application, NSDictionary launchOptions)
        {
 Window = new UIWindow(UIScreen.MainScreen.Bounds);
            // set our root view controller with the sidebar menu as the apps root view controller
            Window.LaunchViewController= new LaunchViewController();
            Window.MakeKeyAndVisible();
            return true;
}

then I add a storyboard reference to my Main.Storyboard, which had Navigation and root my first viewController as LoginViewController, add a segue to show my LauchViewController from Second Storyboard.

Now is I run them together, only the launchviewController works, and the first login page is missing.

Could anyone help with that?
Or please suggest a better login->sidebarnavigation logic.
Thanks!

BTW, I am using the visual studio 2015 for this ios application