Open the first app or window
Press and hold the maximize button at the top right of the window
Drag the window to the left or right side of the screen
Release it when the outline appears
Open the second app or window
Drag it to the opposite side of the screen
Release it when the outline appears
Adjust the divider in the middle to resize both windows
To exit split screen, drag a window away from the side or click the maximize button on a window