If you are using something like a game recording program while you are playing you can take a screenie with the hotkey it is set to.
But at the right hand side of your keyboard above the Insert key near Home.
You should see a key called Prt Scrn
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Sys Rq
Just push that, it's how I take my screenies.
Then go into a program like Paint and then paste it to a blank page and there is your screen.