Hp compact sleep and screen brightness buttens?

on on F keys their a is a sleep button with a pic of a moon on it when i press it it does nothing do i need to press a combo to make it sleep and on the F keys their is two buttons for screen brightness when i press those it dos not change the screen brightness how do i do itHp compact sleep and screen brightness buttens?
These are all boxed items, and should be pressed in conjunction with the Fn (or Function) key, located on the lower right of the keyboard.

dual boot laptop

single beds