How do I change wallpaper on my PC?

First of all, right-click an area on your desktop and choose "Properties".
Then select "Desktop" and you'll find a list of images to use for wallpaper.
Click the background you want from the list and it will appear in the preview screen.
You can choose to Center, Tile, or Stretch the image to fit the screen.
Click OK, your image will be appear on your desktop.

You can use any image on your computer as wallpaper?
See the "Browse" button?
Click it and it should bring up "My Pictures"
where you can use anything you see, or you can navigate to any folder and grab a photo.

Click "Apply" if you want to see how it looks before you close the dialog box,
then OK if it looks right.