Its pretty straighforward and covered in the manual. An excerpt (there is a picture in the manual):
To replace one of these bulbs:
1. Open the liftgate. See Liftgate on page 2-13 or
Power Liftgate on page 2-14.
2. Remove the convenience net, if the vehicle
3. Remove the two taillamp hex nut covers.
4. Remove the two hex nuts holding the taillamp
assembly in place.
5. Pull out the taillamp assembly.
6. Turn the bulb socket counterclockwise and pull it
straight out to remove it.
7. Replace the old bulb with a new one.
8. Reverse Steps 3 through 6 to reinstall the taillamp
When reinstalling the taillamp assembly, make sure
the plastic pin on the taillamp assembly lines up
and is inserted correctly into the opening of