Microsoft wireless laser desktop 4000?

ok, so my father got the desktop set today and has been screwing around with it the whole day. i'm not actually allowed to touch this thing so i can't fix his problems which he keeps firing at me so i'm going to rely on the people who probably do have access to the keyboard. apparently he's been having problems with the sleep function as he doesn't know how to wake it up. could anyone please tell me (who'll subsequently tell him) how to wake up the PC after putting it into sleep mode with the keyboard? Thanks heaps.