Wrong Host. It is the button to the right of F12, which is PrintScrn/SysRq. Thats all you need to press. Then open your choise of editors and ctrl+v. then save.
Invis, You do ctrl-v or File>paste in an Image editing program.(paint works) from there do you File>save save it to what you want (filename) and the extension should be either jpg or png. YOU pick where it goes.