- Download and install Xcode 4.5 GM. Set a 4-inch launch image for
your app. This is how you get 1136px screen height (without it, you
will get 960px with black margins on top and bottom).
- Test your app, and hopefully do nothing else, since everything should work magically if you had set auto resizing masks properly. If you didn't, adjust your view layouts with proper auto resizing masks or look into Auto Layout if you only want to support iOS 6 going forward.
Also note: The auto-rotation API has changed completely, take a look at that as well if your application supports any rotation other than default.