I'm guessing you mean a screenshot.
There are a few programs out there but you can hit print screen.
Go to microsoft Paint, and paste it in to that.
1. Press Print Screen (Or Alt+PrintScreen keys to take just a specific window)
2. Open MS Paint, Either Start, Programs, or start run and typing mspaint
3. Press Ctrl+V or go to edit and paste.
4. Save the image.