Remove the rubber cap (largest one).
Reach round into light housing and you'll feel a flat peice of plastic at a slight angle like this /.
Turn it anti-clockwise about half an inch and hey presto, the bulb carrier will pop out.
The bulb itself will just pull out of the carrier and replace it with the new one(it'll only fit one way)
DO NOT TOUCH THE BULBS WITH BARE FINGERS! as this can cause condensation.
Reverse the above to refit
