If already turn on "Swipe up on Home button"
1. Setting -> Display -> Navigation bar -> Navigation bar -> Check "Navigation bar/Navigation gestures" is on.
2. Open two Apps you would like to use.
3. Press square button next to Home button to check all Apps opened.

4. Click "Split screen" icon

5. System will display 2 screens. Click another App you are going to use in second screen.
If already turn on "Swipe up on Home button"
1. Setting -> Display -> Navigation bar -> Navigation bar -> Check "Swipe up on Home button" is on.
2. Open two Apps you would like to use.
3. Swipe up from the bottom to check all Apps opened.

4. Click "Split screen" icon

5. System will display 2 screens. Click another App you are going to use in second screen.