I don't know if the Kia Rio is towable 4-down or not. It may be if it is a manual transmission. A good place to check is Remco Towing. If it is an automatic and is not towable, Remco may have a solution such as a transmission lube pump.
The lights of the towed vehicle must be run from the motorhome. You can do this several ways.
#1 - you can use magnetic lights.
#2 - you can tap into the towed vehicle's electrical system and use the existing taillights, brake lights and turn signals. To do this, you need to cut the wire to each of the towed vehicles lights and insert a diode to prevent back flow into the vehicle's electrical system. Diodes only allow electricity to flow in one direction.
#3 - you can drill holes in the taillight assemblies of the towed vehicle and insert auxiliary sockets with separate bulbs that are wired from the motorhome.
If you scroll down THIS PAGE
to the section called "Wiring," there are installation instructions for the universal wiring kit (with diodes - option #2) and the bulb and socket kit (separate bulbs and sockets - option #3). Kits are also available from other sources, but the instructions will give you an idea of what is involved.