The base plate is an engineered anchor point installed on the frame of the car to attach the tow bar to. It is usually behind the plastic bumper cover on the front. If you look up your car on the Trailer hitch, hitches and bike rack (800)298-8924
website, you will see a picture and often instructions on what it takes to install it. I had noticed on some of the links about your Kia that the ignition had to be turned on to unlock the steering wheel. (not uncommon) The car's battery can be drained after a day of towing with the ignition on, especially if your towed brake system needs power to operate. Connecting a wire with an in-line self-resetting circuit breaker between the RV chassis battery and the towed battery, using an unused pin in the tow harness is how I solved this issue with my VW. Yes, you can buy a $100 system like this:
LSL Toad Charge Battery Charger
but I find that the alternator and voltage regulator on my RV keeps the towed battery charged as if it's another battery in the chassis battery bank, no need for the extra electronics.