Position new armrest on door, tighten screws if you need too (optional). Where the upper screw portion of the armrest is, trace around it with pencil. Then remove the armrest. Place the new trim in the door and make sure the outline is centered in the opening of the trim.

Very carefully cut a small X inside the outline you drew in step 3. If you push in on the area, you should feel it give in a little around the bracket behind the panel. Start in the center and work your way out to make sure you do not cut too far. The panel is just fiberboard and is easy to cut through.

The hole should allow the upper bracket of the armrest to go inside the panel and rest against the bracket in the door.

Here’s what it looks like behind that panel.