One wire need to be routed to a 12 volt power source. I recommend splicing the wire into your cig lighter, or running it through the firewall and under the Hood
and connecting it to something there.
The ground wire can be connected to a wire with a black line on it in your cig lighter, or can be run through your firewall, under your Hood
, and connect it to the negative battery terminal or someother grounding point (metal frame of your car would work).
So in short, the wires that need to be connected to a 12v source you can run to your cig lighter, and the grounds can be taken there and hooked up to a ground wire, or connected to the negative battery terminal. Just unscrew the bolt holding it to the battery, and stick it in there, and screw it back in.