Open the first app
Swipe up slightly from the bottom to open the Dock
Touch and hold the second app in the Dock
Drag the second app to the left or right edge of the screen
Release it when the Split View window appears
Adjust the divider bar between the two apps if needed
To switch apps in Split View, swipe up slightly to open the Dock and drag in a different app
To close Split View, drag the divider all the way to the left or right edge
If needed, enable multitasking in Settings > Home Screen & Multitasking > Multitasking
Use an iPad model and iPadOS version that supports Split View