Just press the Prnt Scrn key on your keyboard and a screenshot will be
copied to the clipboard. Then just paste it into a graphics application
such as Paint or Photoshop and you can save it.
Pressing the <PrtScn> key copies the entire display to the
clipboard. Pressing <ALT>+<PrtScn> copies only the active Window to
the clipboard. To view the screen capture, open a graphics program,
such as MS Paint, and press <CTRL>+V. This will paste the contents of
the clipboard (your screenshot) into the open file, and allow you to
view it or save it as a file for later use.