Open the app you want to use.
Swipe up from the bottom edge to open the Dock.
Drag the second app from the Dock onto the screen.
Release when you see the split-view divider.
Adjust the split by dragging the divider left or right.
Exit Split View by dragging the divider all the way to the left or right, or by tapping and holding the divider and selecting Close Split View (if shown).