When I bought my Wrangler, one of the first things I missed was the GPS on the dash. I did a little research and decided how I was going to install one in my 2012 JK 2-door. The GPS unit runs on 5 volts from a USB plug. The cigarette lighter plugin has the circuit board to convert the voltage and the USB plug on the other end. Pry open the plug's plastic cover and solder your new power (center) and ground (side) wires to the circuit board. Wrap it all in electrical tape and you're good to go.
Parts stores such as NAPA have Add-a-Circuit adapters to plug into the fuse box for power. I used this to tap into the 12 volt power under the hood. Choose a fuse that is turned on and off by the key so the GPS will turn on and off with the car. I used the interior light fuse with a 2 amp fuse for the GPS.
Run the wire out of the black box and into the engine compartment. I just shut the lid on the wire but you might want to drill a channel or hole for the exit. A few zip ties while running the wire along the firewall and the power is on the driver's side.
I used a long artist's brush handle to poke a hole through the foam in the firewall. It's only a few inches deep so anything thin will do. Once the wire is fished through the foam a couple of drops of RTV or "Great Stuff" will re-seal the foam.
We now have 12 volts positive, fused, inside. I spliced the voltage converter to the power and grounded it at the speaker mount screw. I kept a few feet of wire for a service loop on the interior in case I want to move the GPS to the center of the dash sometime. The USB connector runs nicely up behind the tweeter. Zip tie the wire package and put the panel back on.
I mounted the base with double sided tape from Home Depot. I placed it so I could have my Garmin 1390 for street or my 60CSx when I needed a TOPO offroad.