DevilsAdvocate
First time out of the vault
It's not a switch, it's a "pot". It'll look like some type of rotary switch though: look for anything that looks like it's supposed to turn. Sorry I can't help you any better, but these things can come in literally EVERY shape and size. More than likely, it will be a small silver square with what appears to be a tiny screw inside of it that you can turn with a flat head screwdriver (that's how it looks on MY board).