That depends on what you are planning do do with the port to some degree. If you want power all the time you can use a battery power pink wire from the BCM. If you only want power to the plug when you have the key on find a BCM wire to plug into that is key power.
You will want to make sure the circuit is rated for the amps you want. if you want to use a cigarette lighter then you will want a larger amp circuit. If you just want to charge a phone, most circuits should be able to handle it.
If the donor was similar to my '07 LSJ I can find a few options for you when I get home.