Before we took our cat on its first trip, we left the RV door open and encouraged him to come inside with us. We let the cat become comfortable with the new surroundings - he was used to travel in the car already.
We also introduced him to a harness so that he could go outside on a leash at c.g.'s,. He was 4 years old when we did this, but he adjusted and learned to tolerate the harness. In fact, he would calmly sit at the RV door and wait for the harness before making a dash outdoors.
The cat used to sleep on the bed when we traveled and would come up front and look out the window. He adapted very well and traveled with us for 12 years. He made all the way to the Arctic and to the tip of the Baja and from the Newfoundland to British Columbia. We could not have had a better passenger. Unfortunately at 17, we had to put him down due to health issues. We still miss him.
Good luck with training your new kitty.