ok i was fiddling with this today because it wasn't fitting flush, i think it got bent by the thieves who broke in. If your removing it, there is a black plastic tab that goes in right underneeth the side mirror. So after you pop it up using a door trim removal tool - pull it to the left towards the rear of the car so you don't break the tab.
Theres also a black flat holder the on the other end of the by the lock that the end of the chrome trim wil be set in.