how to split the screen with 2 or more apps

Here's the instruction Use two Mac apps side by side in Split View - Apple Support

You haven't told us which OS you are using. You may not be able to use split screen with your machine. Can you complete your profile with details of the OS you have and the version / age of your machine . Otherwise we are reduced to guessing.

You might also include the application and their version numbers since there are applications that don’t support split screen even though the OS does.