Instructions: Right-Click the desired size, and select "Save Target As..."
Then save the wallpaper where your desktop wallpaper is
usually saved. (In Windows it is: C:\Windows)
Or, you can click on your desired size and a window will pop-up
displaying the wallpaper full-size, and you may save it as you usually
save pictures on a webpage. (windows: Right-click picture, Select
"Save Picture as..." and save it in C:\Windows)
Then go into your display properties and select the wallpaper
which should be one of these file names: