WINDOWS:
1. Right-click on the image and click"Set as Background"

MAC OSX:
1. Drag the image off onto your desktop
2. Go to system preferences
3. Go to your Desktop icons and open it
MAC OS9:
1. Drag the image off onto your desktop
2. Go to your control panel and choose "Appearance"
3. Click "Set Desktop" and choose the newly downloaded image on your desktop
4. Choose the "Collection" drop down and "Choose Folder" to find the new wallpaper on your computer