the two long screws that go into the light housing, put in outer holes on the bracket, slide springs over them and screw into light housing. Then on the plastic inserts, shorter screws that came with the bumper(hole in the plastic cover otherwise) go thru the plastic inserts into the metal bracket. Boom, done they're mounted. Make sure to take the inserts off instead of attempting to mount on the vehicle.
The wiring, I cut my factory foglight harness off(lights side, not vehicle side), cut the ends of the ARB harness, did some connecting and the fogs now plug directly into the OEM wiring. I didnt see the reason to need to add the whole ARB harness as the fogs are only 55w just like the OEM fogs.
I guess you could get some bullet connectors actually and wire the OEM plug with the pigtails you create into your IPFs. I was too lazy to find them, maybe one day I will if I feel like cleaning it up.