Click on the size you would like and after the image has loaded, put the cursor
on top of the image, hold down the right mouse button and select set as
wallpaper or set as background on newer versions of
Click on the size you would like and after the image has loaded, hold down the
mouse button until a pop-up menu appears allowing you to save image
as to download. When the image is saved, use the System Preferences
Desktop control panel.