In order to access the Split Screen, you will use the Split Screen handle, (a green box with a small white arrow inside). This can be found at the side of the screen when in landscape mode, and at the bottom of the screen when in portrait mode.
Simply tap on the Split Screen handle and drag to open the Split Screen. You can adjust the size of this window to any size, at any time.
As you navigate through a Bible in the main window, the split screen window will stay in sync if you have a versified text open in the Split Window. Such as another translation of the bible, or a commentary.
Other options for the split window, are to open your Notes, Highlights, or any other title in your library.