Split the screen on an Android phone

Open the app which you want to show in split screen then tap 3 vertical lines at bottom left so that you get the screen below

Now tap the icon shown in red square below (in this case the text app)

You should get a screen something like this

So click open in split screen mode, then you will either get ‘select the split screen app’ and a range of apps to select from, or you might get this screen, depending on your model of phone

In which case swipe left or right to find the app for the other half of the screen. 

To revert to single screen just press the < bottom right