you need to replace the bulb or the whole lens assembly? Inside the cargo area there should be access covers behind each tail light... to replace a bulb all you have to do is pop the cover off and turn the socket counterclockwise to remove it... then just replace the bulb and lock the socket back in place.

To replace the whole lens, there will be 4 8mm bolts holding the lens in place, you should be able to see them with the access cover removed. Remove the nuts and pop the lens out of the car...its pretty simple.