Making a 4 wire Voltage Reducer "keyed"?

I purchased a Tecscan VOLTSeasy which converts 48V to 12V (15Amp). There are only 2 in and 2 out wires though (no switched yellow). Is there an "easy" way to wire it to my keyed switch on a 2011 Precedent?

Doing a search I came across this thread, but that doesnt fit into the "easy" category for me :-) :
http://www.buggiesgonewild.com/elect...y-reducer.html