HOW TO :
Windows Users
1. Right Click on the picture with your mouse and choose 'Set as Background'
OSX Users
1. Right Click and Save
2. You can keep the image anywhere you want, but I'd suggest you keep your wallpaper files in /NameOfOSXDrive/Library/Desktop\ Pictures/
3. Click on the Finder, then from the menu click Finder > Preferences...
4. Click 'Select Picture'
5. Select what you want and click 'Choose'
Linux Users
1.Right click, select save image as, choose where you'd like the image saved, save
2.If you are running Gnome you can use the Gnome Configuration Tool (gnomecc): Desktop -> Background -> Browse, then select the image you downloaded.
3.If you are running just about any other window manager, you can use the command line tool wmsetbg.