I just spent about an hour trying to figure out the same question.
What you need to do is take the access door off. It is a plastic round door inside the wheel house. (It may help to turn your wheels in the opposite direction of the side that the bulb needs replacing so you can access the door a little easier). To take it off just push in the 2 plastic clips and give it a quarter twist and it will come off.
You then put your hand up the access door and turn the socket for the bulb half a twist. I couldn't figure out what to turn at first as I couldn't see what I was doing. But it helped to get a mirror and see where the socket was and how it needed to be twisted. Once the socket is turned it should pull out. Pull the socket and the wires back through the access door. Replace the bulb and then install the same way you took it out.
Hope that helps.