How Do I Open the panel where the headlight switch is locate

[wbras]

Recently a local electronics store installed an aftermarket door lock system in my 2002 S60. They showed me, from a distance, that they had placed the sending unit in this panel which was pulled out like it was a drawer. Now it rattles and I can't seem to get them to look at it again. But it seems a simple thing to check but I can't get the panel to open. Does anyone know how to get this thing to release and pull out so I can fix the rattle noise that's coming from the panel box?