A trim removal tool is useful here but if not the panel can simply be pulled up with care. The plugs are the same fixings that hold the main door cards in place but instead of 'locking' into position, they are used in a compression state instead. The chrome and plastic panels are both fixed the same way by plastic plugs.
If both panels are to be removed then the rear tailgate lock panel should be removed, if only one side is to be removed then the panel can be lifted slightly on that side if preferred. The procedure is largely the same for both sides with a few subtle differences:The panels are held in place by a number of screws, clips and adjacent panels.
This guide talks through removal of the rear quarter panel 'door' cards.
