Runescape Keyboard setup

Hi Guys

I am trying to use the function keys on my keyboard for quicker switching between inventory, prayers and special attack. For some reason, it does not seem to work for me., Any ideas on how i set this up? My keyboard is set to standard US. Many thanks in advance.

Sometimes I use the F keys when doing stuff that requires getting around the interfaces quickly, like pking, nex, etc. What I do is I just put my left hand on the F keys, and my other hand on the mouse and use the middle mouse button to control the camera.