If youre running Windows 7 or Windows 8, right-click on the desktop and click Screen resolution; in Windows 10, click Display settings. This will take you to a screen where you can configure the options you have for multiple monitors in Windows. Here, you can confirm that all your monitors are detected.

How do I split my screen into 3 monitors?

To split your screen into 3: To include a third window into your screen, drag that window to any corner of your screen and, you will see an outline. Then, release the mouse button and it should fix in place. Now, you have 3 windows occupying your screen.