Hey there 2CV, it was me, I'm the guy that installed those horns.
When I un-wound my harness and dug out the horn wires, they were long enough to reach my left side tool box where i mounted the relay. I ran the negative from the stock horn switch to the 85, ran the positive from the stock switch to the 86. Then a inline fused line from the battery to the 30, then a new hot wire on the 87 going to the horns.
So
Terminal Lead
85 Horn Switch Neg
86 Horn Switch Pos
87 New Wire to Horns
30 Inline Fused Wire to Bat Tree
Hope that helps, have you wired them direct to hear what they sound like yet? They're LOUD huh?