579 wiring question.

On 389s there's a couple dead end harnesses under the hood that's rolled up under the fuse box that connect to the switches on the dash. Look for one labeled "option power" and another one is labeled "sleeper/cab lights"
I'd assume the 579 is wired the same

 

Yes look at the harnesses underneath that fuse box to see if there's any wires that arent connected to anything. There maybe a couple that are from the switch

 

If you have the aux switch, it powers a wire harness under the fuse box that has a sticker attached labeled cab/sleeper lights, this is what my chix lights are connected to.
The switch with relay switch powers that wire I was holding in the first pic I sent, both harnesses are next to each other underneath the under hood fuse box on the drivers side.
I haven't found where the rest of the spare switches lead to

 

Yes, in that mess is where the switch wires were located on mine, they were coiled up and zip tied.
Another option for you if nobody else has proper 579 info is- check under your bunk inside the sleeper door on the drivers side, you may have a large terminal/junction block inside that has wires running to it. Sometimes this box is located under the truck on the frame somewhere. It will have wires connected to studs labeled- turn signal, brake lights, marker/clearance lights etc. You can add your chicken lights power wire to the marker light terminal stud and they will work with your truck light switch instead of the "spare switch". The terminal block looks like this-

 

How do you get the power turned on to the spare switches? I have 5 spares but none of them light up when switched on

 

If they don't light up then you probably don't have harnesses connected to them. You could buy the harnesses or make your own, I don't know what each terminal does but they should be easy enough to figure out by testing the terminals continuity with a multimeter and moving the switch position