First of all, I did this while wiring up my projector headlights but offroad lights would be the same. The wiring that came with my projectors already came with a relay so that step will be left out.
Step 1: Choose where to mount the toggle switch and drill a hole.
Step 2: Splice a wire into the W/BL wire coming out of the headlight switch, this wire is actually for the daytime running lights. If your toggle switch comes with a LED light find a ground.
Step 3: Connect the power and load wires and the ground wire to the toggle switch.
Step 4: Put the toggle switch in the hole that was drilled. Now the offroad lights can't be left on without the running lights also being left on.