I don't have the diagram right now, but the basic plan is to "splice" it into the hot & neutral wires before they enter the controller. In my case, I just inserted a pigtail into the hot wire just before it entered the controller, and I tied the neutral together along with all the other neutral wires.
I will look for the diagram and if I find it I will post it a bit later.
Beer is like porn. You can buy it, but it's more fun to make your own.