Just so, how do I split screen on Mac OS Sierra?
- In the top-left corner of an app window, click and hold the green button, drag the window to the side you want, then release the button.
- On the other side of the screen, click the second app you want to work with.
- In Split View, do any of the following:
How do I split screen on Mac with a monitor?
- Connect and turn on your additional display.
- From the Apple (?) menu, choose System Preferences.
- Choose Displays.
- Click the Arrangement tab.
- In the lower-left corner of the Arrangement pane, select "Mirror Displays."