OK let me start with I have a '94 but the idea is the same but wire colors are different but a multimeter will tell you what wire does what.
Tap your switched power, for the toggle switch, into the parking lights wire behind the headlight switch. This will allow for the lights to be turned on anytime the parking lights are on and will shut them off with the head light switch. I tapped into the the yellow wire coming out of the '94 headlight switch and ran it to my driving light toggle switch so if I don't want them on with the parking/headlights I can turn them off.
Using a relay is necessary, allowing low amp switched power to toggle high amp power for the lights. I personally used the under hood existing wiring for the relay and wiring to the bumper. I taped into the wire in the bulkhead connector to energize the circuit as I didn't have the cab wiring for the driving lights. I do not know if this wiring is existent on your '91 or not to use it. If not there you will need to run more wires and install a relay and fuse into the circuit.
Having it this way allows for all exterior lights to be turned off with the headlight switch preventing driving lights being left on. Hope this helps. There is also a writeup the tech section on this but meant for my gen of ranger but the steps are the same for the most part.
EDIT:
https://www.therangerstation.com/tech/rewire-fog-lights-to-work-with-all-light-settings/#gsc.tab=0
Since I didn't have the cab wiring this writeup didn't help much but gives an idea of what to do if you do have it.
DISCLAIMER: Activities and vehicle modifications appearing or described at The Ranger Station and it’s pages may be potentially dangerous. We do not endorse any such activity for others or recommend it to any particular person – we simply describe … Continued
www.therangerstation.com
This link will help finding wiring diagrams for your ranger to help plan out what wire does what and where it goes to.