Start out light and easy. Of you're really out of shape, it almost doesn't matter what you do, as long as you do something. Some sort of frequent
aerobic exercise for fat loss. Some kind of weight exercise for muscles. Walking/jogging/biking/treadmill, etc for the aerobics. Push ups, sit ups of crunches, body weight squats, dips between two chairs, etc. for resistance exercises. This should do you well for a couple of months. Then you may find you need to increase the intensity a little.
If you're in an RV, I guess buying a lot of equipment isn't an option, right? You can go pretty far with some
dumb bells, resistance bands, chairs, and a pull up bar... Pull ups are tough, but you can rest your feet on the ground and pull up as much body weight as you can. You can also rest the pull up bar across the backs of two chairs, lie on the floor beneath them, and do sort of an inverted row keeping your feet on the floor.