how do I remove rear light cover

I have removed the two screws that hold cover, but I can't seem to get this cover off... What else needs to be done to replace the rear brake light bulb?

Any help would be great..
Thanks
Sharon

REMOVAL
Disconnect and isolate the battery negative cable.
Open liftgate, remove two hex head bolts in inner D-pillar, Rotate lamp outboard away from vehicle to remove tail lamp forward stud from grommet.
Disconnect electrical connector.
If replacing the tail lamp unit, transfer lamps to new unit.