The Multi window feature allows multiple apps to be run on the current screen at the same time.
From a Home screen, tap the Recent apps icon (lower-right).
Scroll left or right to locate the preferred app then tap the app icon (e.g., calendar, gallery, email) located at the top of the panel.
Tap Split screen .
From the Recent apps screen tap the second application preview to be used.
When on, tap the Recent apps icon (lower-left) to change the current app.
Adjust the size of the apps by sliding the horizontal bar between the apps up or down.