On most computer applications, F1 is the keyboard shortcut to bring up the help menu. Thus, the phrase "Press F1" is most appropriately given as a reply to anybody who needs help, especially in the psychiatric sense.
<Joe> Oh my god, at lunch today, everybody stopped talking and I said, "Crap, the chat died." I really need to stop wasting time on IRC.
<Phil> Dude, you really need help. Seriously. Press F1.