how can i use split screen on the ipad

Depending on which Apps you are trying to split it may or may not work. Not all Apps support split view.

See here for how to get Apps into Split View: Use Multitasking on your iPad - Apple Support

Basically, once you get the second app in Slider Over, you need to drag down the grey handle at the top to engage Split View.

Maybe you need all of this to help you properly learn to use and navigate iOS 11.

iPad User Guide for iOS 11 by Apple Inc.

https://itunes.apple.com/us/book/ipad-user-guide-for-ios-11/id1263310093?mt=11

Another very good iOS 11 Users Guide

https://arstechnica.com/gadgets/2017/09/ios-11-thoroughly-reviewed/

VIDEOS!!

iOS 11 Basics

https://www.youtube.com/watch?v=cnEfNBQ_F1Q&list=WL&index=81&t=904s

https://www.youtube.com/watch?v=_rgnwfgHXSg

iOS 11 Dock

https://www.youtube.com/watch?v=i2eXus8fweg

https://www.youtube.com/watch?v=MBoeJCmxnpA

iOS 11 Multitasking

https://www.youtube.com/watch?v=JsAh2EjyIVo&index=83&list=WL&t=8s

Good Luck to You!

What iPad model do you have?

Certain iPad models cannot do split screen view.