Use the sidebar to open freeform apps in a small window that you can move and resize.
Go to Settings > Gestures.
Tap Sidebar and turn Use sidebar on 
You'll see a sidebar on the right edge of your screen. Swipe it in to see a menu of apps that you can open.

On the sidebar, tap 
Or, go to Settings > Gestures > Sidebar > 
Customize the menu:

