So far as its power goes, Basic Radio Installation 101 guidelines are that you always power a 2-way radio directly from the battery. Other sources of power like the fuse box, cigarette lighter, etc. are notoriously electrically noisy from things like the fuel pump. If you have a manual transmission, there is an unused rubber hole plug just above the accelerator pedal on the fire wall you can drill a small hole through for running the power wires into the engine compartment. Use 12-14 gauge wiring & be sure to secure it with zip ties as you route it along the top of the firewall along the OE wiring harness to the battery.
An easy way to mount the antenna on the rear of the Jeep is via a bracket that goes between the tail light and tub. Tera at TeraFlex Driver's Side Antenna Mount
makes them for both the passenger and driver's side tail lights. That link is for the driver's side but they make one for the passenger side too.
Mounting-wise, the TJ doesn't make it easy. My first CB mount was to the center rollbar hoop via self-tapping screws. The CB was mounted facing forward in the center of the rollbar so I could hear it easily and see what channel it was via the rearview mirror. It was out of the way yet the microphone could hang straight down and be placed in a cup holder for easy access.
Finally, take great pains to assemble the antenna mount EXACTLY as the instructions describe. 99.9% of all CB problems are because the antenna mount was assembled incorrectly. When that happens, the antenna shorts directly to ground. I pulled into Carl's Jr. parking lot a few days ago to have a hamburger & couldn't help but notice another Jeep whose antenna mount was misassembled. When its owner came out, I asked how his CB worked and he admitted it didn't work. I pointed out his mount issue to which he said he had been trying to make his CB work for years but never checked the mount.
There's more to getting the antenna working properly but we can help there when you get to that point.