Right click on the image and "Set as Wallpaper"
if this option is available. If not, choose "Save
Image As", then choose a file name and add
".jpg" (Save the image to your desktop so it is
easy to find)
From the Start menu, go to Settings, Control
Panel, then Display, then Background - choose
"Browse", go to "Desktop", then open the "jpg"
file and Click "OK"
Mac Users
Holding Ctrl and clicking the image
simultaneously, choose "Download Image to
Disk" and save the image to your hard drive
Choose Apple menu > System Preferences and
click Desktop & Screen Saver
Click Choose Folder and navigate to your
wallpaper image
Click "Choose" to confirm your choice.
How to Download Screensavers
Save the file to disk and when prompted click "Open" and follow the instructions.