1. Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings.
(If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, click Settings, and then click Change PC settings.)
2. Tap or click Accounts, and then tap or click Your account.
3. Pick one of the following options:
Find a favorite photo. If you want to find a favorite photo to use, tap or click Browse. You can navigate to photos on your PC, or to pictures you store on SkyDrive. Tap or click a photo to select it, then tap or click Choose Image.