Ah - good choice - this is one of my favourites! I suppose you what to know how to get it on the desktop now. There are more that one way to skin a cat when it comes to setting the wallpaper / bcakground as your desktop. You can either right click desktop wallpaper beow and then select 'save target as...' (IE & Opera) or 'save link as...' (Firefox). If this is your chosen route, remember where you save it! Next goto where you set the desktop background for your particular computers operating system and select the image from the location where you saved it.
A different way altogether is to right click the background below, from here choose 'save image as...' or 'set as Desktop Background' or 'Set as Background'. You'll know what to do when the time comes. I trust you. You probably already know in fact. I'll keep a lid on it now.
Return to wallpaper thumbnails.
