Grab a factory service manual with wiring diagrams, or if you're friendly with your local dealer, see if they'll make copies of the pages for you. Or...if you're just adventurous, start looking around in the dash and see if you can find wires that aren't attached to anything. If you have a good multimeter, tone out the wires (one meter lead at the fuse, one meter lead under the dash, it'll beep for continuity) to be safe.
My 92 didn't have factory fogs so I don't know where the switch is when they do have them, but I'd guess it's the little black panel to the right of the column. The whole section from the HVAC to the speaker pops out with just a couple screws, so you can look around pretty easily.
Worst case, get an install kit from an auto parts store or 4x4 store (should be wiring, a relay, and a switch/fuse) for about $20, lop the connectors off the lights themselves, wire up the new harness, and install your switch. Since mine came without, I wired up 2 sets myself. Nice thing about wiring them yourself is, you can set them however you want. I have 2 small fogs that are ignition-switched as DRLs (on whenever the key is on, have a switch on the dash to override if I want to turn them off), and I have 2 OEM fogs mounted center, wired to come on with high beams (also with an override switch in the dash to turn off if I want). Your factory lights, if you use factory wiring, will turn off whenever you toggle your highbeams.