This pic may help
Lights have a ground wire and a power wire
Relays manage power, as a Switch cannot take the high amperage required to power lights. Relays have four wires
- Ground wire to chassis (#85)
- 12V power wire to battery (#30)
- 12V power wire from switch (#86)
- 12V power wire to light (#87)
Switches connect/disconnect power and have three wires
- Ground wire to chassis
- 12V incoming power wire. This can be from battery, from a switched source (like windows), from an always on source (like 12V accessory sockets)
- 12V outgoing power wire to switch
Switch
First, find a place for your switch (and find a switch). Many H3 owners use the blanks by the wiper control. Bigunit has the part # for the OEM switch.
Second, find a ground. I recommend running a wire to the firewall by the steering column. There are a few ground points in that area used by the factory
Third, find incoming power. I recommend tapping into the 12V accessory socket right next to where your switch will be
Relay
First, find a place to mount the relay. A good place is on the firewall inside the cab, using the studs in the firewall by the steering column
Second, run a ground. Use the same ground location as you used for the switch
Third, find power. You can't use the same power as you used for the switch as the lights draw a lot of current. I recommend buying an "Add A Fuse" at Auto Zone, putting it in an empty spot in the fuse box under the hood, and run the power back through the firewall to the relay
Fourth, run one power line to the front where the lights will be. You can then split that one line into two for the two lights
Lights
First, find a ground. You might run it back to where the fuse box is grounded
Second, use the power from the relay.
Firewall
I found it easier to drill a new hole in the firewall and run my wires through there. Be sure to drill a big enough hole to use a rubber grommet (pick it up at Ace Hardware) and seal the hole afterwards with RTV sealant. To gain better access to drilling for the firewall, remove the knee bolster.
Of course, I should ask - did these lights come with a wiring harness or do you need to start from scratch? What was included?