Decide where you want the switch. I wanted mine on the short side of the tin. Since I'm using a rectangular switch, I need a dremel to cut a notch in the side of the tin. Use a marker to mark where you need to cut. You need to cut between the edge of the actual slider and the screws. This way, you can slide the switch freely and still have a place to screw it in on the tin. Be sure to wear safety goggles because cutting the tin with a dremel does produce sparks. After you cut the notch, put the switch in a drill tiny holes where the screws will go. Screw the screws in until everything is nice and tight.