How do I remove a split screen on my iPad?

Key to accessing and controlling multi-tasking is the small “three-dot” button that is found at the top-centre edge of each App Window. Tap the multitasking button at the top of the slide-over window to expose a menu - from which you can change the window view.

More information about using multi-tasking can be found in this support page:

Use multitasking on your iPad - Apple Support

The iPad User Guide is also a rich source of information about using iPad and its many features. The Guide is available both online using a web browser (such as Safari):

iPad User Guide - Apple Support

You should note that some Apps are designed to have what appears to be a split view within the App. Where applicable, this is not a multitasking split-screen view as it is within the App itself.

Tap the three dots at the top of the screen you wish to close. Select Close.