ARB has about the best pre-packaged wiring kit for fridges. It comes with a socket that can be used as a regular cigarette lighter plug or there's a slight modification that makes it a locking plug. I'd guess your fridge comes with that type of plug.
The stock wiring will run it and I've seen a few threads on modifying it to constant on. However, the wiring is small so there's a lot of voltage drop between the battery and rear cargo area. You're much better off in the long run to just run a dedicated line.
https://www.4wd.com/p/arb-12-24v-dc...fgLbL3gL-GE3-teN8bc8gnwNsvJvoBHhoCBq4QAvD_BwE
I went overkill and skipped the kit/plug and just ran 8awg from the battery to the rear with an anderson connector. These are non-gender specific yet polarized plugs that basically can't vibrate loose. I went with the bigger wire assuming I might add some additional lights and such in the rear in the future and would need a ready source of constant 12V power. Up front it's fused near the battery.
Find yourself a good youtube video or thread on running the wire. On my 4th gen the main harness runs along the floor under the driver's side door sills. Not sure if it's the same on the 5th gen. This is the most straightforward place to go then you don't have to mess with the carpet and such. There are a few unused rubber grommets in the firewall to get you through to the engine compartment and battery. About any car audio shop can help you out with the process too.
Good luck
