ON A PC: RIGHT-CLICK ON THE IMAGE AND CHOOSE "SET AS WALLPAPER"

ON A MAC: RIGHT-CLICK (or Control+Click) ON THE IMAGE AND CHOOSE "Save image to the desktop". ONCE DOWNLOADED, RIGHT-CLICK ON YOUR DESKTOP AND CHOOSE "Change Desktop Background...". YOUR SYSTEM PREFERENCES WILL OPEN - FIND THE "Select Folder..." OPTION THEN NAVIGATE TO THE IMAGE WHICH IS NOW ON YOUR DESKTOP.