I didn't have an FSJ but the install is just the same the 4 light is a little different but the process is the same.
First remove the headlights:
Mount the relays inside in the right (passenger) light socket. Don't mount it in the center of the socket because it will hit the light bulb. Mount it to the right out of the way. The commando is a little different but you get the point. Note the black wire with the self tapping screw coming from the new yellow socket you will see in the pic after this one. Sand off the area below the black ground wire to ensure good connection if area is corroded.
This is the right (Passenger) light socket. The black male plug from the new harness plugs into the old light bulb socket & then tape them together. The light will plug into the new yellow socket.
This is the Left (Drivers) socket: Run the wire from the Right (Passenger) side to the left (Drivers) side to the light socket. The wire will run through the grill area & can be tied to the wiring that is there now. The wire has been taped to make it look OEM. The Left (Drivers) side socket will be identified by locating the socket with the longest wires. Mount the black ground wire as shown. Clean as suggested earlier. Just tape up the old light socket. You will not use it. The light bulb will plug into the yellow porcelain plug on the new harness.
Next you will run the fused wire to the stater solenoid from the relay notice it has a plug so you can disconnect it to make the wire easier to run. Run the wire to the solenoid as simulated & bolt it on the BATTERY SIDE of the solenoid. Now replace the light bulbs plug them into the yellow Porcelain H4 sockets & test them. Your head light & dimmer should work with whatever light bulbs you should want to use.
Yes I know the Commando solenoid is backwards from an FSJ. Thats why I'm ensuring you know to tie it the battery side,
Wiring may be different for the custom units.
Let me know if you have any questions.