Careful with this one - can be slippery when wet. I suppose you what to know how to get it on the desktop now. Getting the wallpaper onto your desktop background can be done in a number of ways. You can either right click the background below and then choose 'save target as...' (IE & Opera) or 'save link as...' (Firefox). If you do this - remember where you saved it! Then go to wherever you set the background for you particular computer / operating system and select the image.
Another way is when the full screen wallpaper has loaded, right click it and choose 'save image as...' or 'set as Desktop Background' or 'Set as Background'. When you're ready - you'll know what to do. I believe in you. I bet you already know. I'll be quiet then.
Return to wallpaper thumbnails.