To change the background of your window, follow the below steps:

1. Open Start by swiping in from the right edge of the screen and then tapping Start. (Or, if you're using a mouse, point to the lower-left corner of the screen, move your mouse all the way into the corner, and then click Start.)
2. Swipe in from the right edge of the screen, and then tap Settings.
   (If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, and then click Settings.)
3. Tap or click Personalize, and then tap or click the background, background color, and accent color you want. The background and accent colors you pick will show up in a few other places too, like the charms and the sign–in screen.

To see your desktop background on Start

1. Open Start by swiping in from the right edge of the screen and then tapping Start. (Or, if you're using a mouse, point to the lower-left corner of the screen, move your mouse all the way into the corner, and then click Start.)
2. Swipe in from the right edge of the screen, and then tap Settings.
   (If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, and then click Settings.)
3. Tap or click Personalize, and then tap or click the preview of your desktop background.