To wire horn relay...
Using common 20 Amp driving light relay...
Terminal 85 goes to 12 v source from old horn. Existing wiring OK to use.
Terminal 86 goes to new ooga horn + using 12 ga wire.
Terminal 87 goes to horn ring to ground when horn button is pushed, existing wirink OK to use.
Terminal 30 fused to battery. Use 12 ga wire.
Ooga horn - to ground using 12 ga wire