switch?

I have the HB4H horns and right now I have the air valve tapped into the stock horn wire, but I want a switch to turn the horns on and off just to be safe.
(like the video here http://www.hornblasters.com/products/details.php?i=hornblasters-4-horn-train-horn-kit)
I think I have some idea on how to do this but I would rather do it the right way the first time. can some one tell me exactly what to do? pictures are always nice as well.

http://trainhornforums.com/showthread.php?t=2181&highlight=stock+horn

Yes I read that, but I still have some trouble understanding as I’m not mechanically or electrically inclined on any level.
from my understanding this would work?
black lines are whats done, red is what is what I think will work (all lines are wires)
the switch being off no power is getting to the air valve so no train horns right?

your theory is correct but i fixed ur drawing cause i’m ocd. that is actually how i have mine done

thanks for the help man, i got my project for tomorrow planned out now

thats what we’re here for.