Right click (left click if you have a left handed mouse) on an empty part of the windows desktop and the menu below should appear. Select Display settings.
When you select Display Settings you will see a screen similar to the one below.
Windows will designate which screen is screen 1 and screen 2 (and more if you have them). Press identify and a box with a number will show up on the bottom right corner showing each monitor's ID number on the monitors.
After you identify them, select the rectangle that designates the monitor you wish to move and move it as you want. Apply and Cancel will appear below the dialogue box.
Click Apply to save changes.
Check if the monitor you want is the main display. The main display is where your desktop icons are placed.
Make sure to open the Display Settings window on the monitor that you wish to use as your main display.
To make a monitor the main display, just click to highlight the monitor then click the check mark box. It may be already clicked.