How do i

[Bellatrix]

Yeah, taking pictures from inside the game is against
the rules, unless it is for reporting a bug. I would not
even think about taking screenies to post on forums,
they may find you and ban you.

If you insist to take a screen shot for reporting a bug,
the Print Screen button will be on your keyboard. Look
on the top row towards the right for a button that says
"PrtScn." Press it, and then open Paint. Paste it into
your document, and they you are done.