Select the link for the dimensions of the picture to download for your screen resolution.
Using the mouse, right-click on the wallpaper image.
If available, choose "Set as Wallpaper" or "Set as Background" from the menu that appears.
If not, choose "Save Image As", then choose a file name and add ".jpg" (save the image to your desktop so it is easy to find).
From the Start menu, go to Settings, Control Panel, Display, then Background - choose "Browse", go to "Desktop", then open the "jpg" file and click "OK".