Step 1: Right click on the desktop, select "Display settings."

Step 2: Select "Extend these displays"

Step 3: Select "Keep changes"

When the changes take effect, the settings of the selected monitor appearing in blue will be displayed.

Rearrange displays and make main displays

The position of the two monitors relative to each other is displayed using the boxes [1] and [2].
To see which number corresponds to a display, select ”Identify”. A number appears on the screen of the display it is assigned to.
Select and drag the display to the desired position and select Apply.