you have to buy a camera, then you have to set your screen so it has a really high refresh rate.. or low.. can't remember which, you set your camera on a tripod and see if you line it all up correctly. take the picture, then you take it to the photo processors, get them to make your picture, you take teh photograph, scan it into your computir and then you have it.
(or you can press the key "prtscn" and then in a picture editing package, select 'paste'. )