Are you talking about the threaded sleeve that is on the upper door panel at the rear quarter window? If so, it would be below the panel cap. That cap can be easily removed. It is held on by one screw in the chrome strip at the rear and (2) push clips. Will also have to remove the upper chrome plate on the door jam facing the rear. I can't remember the the rear seat back has to be removed also.
I can snap a picture later today of what it looks like.