Boot/Trunk Release Button; How to access?

My boot (trunk) release button on the boot lid does not work. The key fob and interior trunk releases work fine. I susspect I need to replace the switch on the boot lid.
How do I get to it? It is behind the chrome trim cowling on the lid. I see three little slots on the cowling, but a small screw diver inserted did not lelease it.

Please tell me how to access my trunk lease?