Need your ideas on how I should handle a rescued barn cat?

I live in a small ranch with over 2 acres of land adjoining a state park. A fifth wheel RV sits on our property. I rescued 14 cats dumped in the park, got them shots, neutered and rehomed 13 of them. One of the female kitties, a one year old is semi feral and I couldn’t find a home for her. I have 3 little dogs and 3 cats in my home and my animals wouldn’t do well with another cat. So, I keep the rescued kitty in the fifth wheel, heated, with cat toys, food, plenty of places to sleep, let her out during the day, visit, and lock her in before sundown to keep her safe. Trouble is she’s isolated and alone, so I’m getting a rescued 10 month old male barn cat to join her. He doesn’t know this area. How do I train him before I let him out so that he doesn’t wander and get lost.