Mac OS X:
1) Hold the CONTROL and click or right click on your mouse on the image size you want. From the pop-up menu that appears, select "Open In New Tab . . . " or "Open In New Window . . . " This will open a new tab or browser window with the full wallpaper image. Go to the newly opened tab or window, hold the CONTROL key and click or right click on the image and select "Use Image As Desktop Wallpaper."
1) After clicking on one of the wallpaper sizes listed below the thumbnail image, a large version will open in a new browser window (make sure your pop-up blocker is turned off). Then, right-click the graphic you want to set as your wallpaper. From the pop-up menu that appears, choose Set as Wallpaper/Background and use the Stretch option to fit your screen. View your desktop to see the graphic displayed.
2) Alternatively, for more advanced users, right-click the image link and save it to your computer. Then right-click on your desktop and select Properties. Select the Desktop tab at the top and select Browse. Find the image saved in your computer and select Open. The image should preview in the box. Select either Stretch or Center in the Position dropdown (depending which one looks better on your desktop) and hit Apply to preview. If you like it, hit OK.