as dubs has said peel back the rubber boot at the bottom this will reveal a 10mm bolt undo this and you can pull the switch out slightly once out get a can of wd40 and spay it down the side of the sprung loaded pin and then rapidly push in and out several times this will help clean up the contact inside you wont be able to pull it right out as it is joined inside the car by a white connector block and the only way to get to this is take the bottom interior panel out by the rear passenger seat once you have pushed it in and out a few times make sure the metal surface is clear and reattach it to the car and if its working your lights should come on if not you can get replacement switches from mr t for these or see if someone has a know working second hand one its easier to cut and just solder the wires together and then heat shrink tube it rather than taking the panel out to get to the plug