Select the resolution you want, then click to download the zip file(s) to your computer hard drive. If you're not sure of the resolution you need, right-click on your desktop, select Properties, then select the Settings tab to find your screen resolution. Once you have downloaded the free zip file(s), extract the .jpg using WinZip or similar program. You can then double-click the .jpg file to open the image, right-click and select Set as Background to make the image your Desktop Wallpaper.