Wallpapers are your backgrounds of your desktop. There are two ways to set it as your background. One is simply to right-click the image and click on the "Set as Background..."..That's the easy way. The next way is to right-click it, then click on "Save Picture As...", right-click on your desktop, go to "Properties", and choose the "Desktop" tab, and click on browse. Find where you saved it on your computer and click on it, followed by clicking "OK". Then click "OK" on the original window, and voila^^. I suggest the first way o.o. P.S. These are thumbnails. Click it to see the full size.