It is on the right-top of ur keyboard, beside the "F12" button. Maybe named "Pr Scrn".
But if u wanna capture anything on the screen, i think the print screen button couldnot help u, press this button, u only get the full screen capture. So i recommend u try PCHand Screen Caputre. It could help u capture anything. Im using it, it is easy to use, even for a novice. I think it is pretty good. Hope it could help.