So simple once you do it, POWER OFF.
Remove the screws from the cover, slide it back, you'll probably have to tilt it slightly and pull the sides out slightly. Doesn't take much effort so don't force it. (Make sure you've taken only the screws from the cover.
Once the cover is off, on the switch side, there's a light fitting with 2 wires going into it (and probably a little sticker with a warning about switiching the power off before removing the light fitting which will help locate it) The light is contained in a little chamber, use a torch to check if you're unsure. Mine had only 1 screw holding it place and was oval shaped. Remove the screw and lift out the fitting and bulb. (If you're unlucky like me, my bulb had fallen out so had to fish it out with sticky tape wrapped round a pencil!!) Relace bulb and put it all back together again remembering that when you replace the cover, tilt it down to the front to ensure the slots are in place. Replace screws correctly. Once back in place it must all be flush with no bulges or bends in the cover. If there are, the slots have not engaged properly. Unscrew and try again. Good Luck.
Handy Mandy, October 2011