Dan is right. When you leave your hands on the top of the steering wheel, you have to turn it the OPPOSITE way from where you want that trailer to go. That's just not natural! If you put hands on the bottom of the steering wheel, you turn the way you want the trailer to go.
Practice will help, and it will get better in time. It's also easier if you can select a space that you drive past it to the left and then back in. You can see where you are going better, and aren't backing to a "blind side". The easiest is to ask for a pull-through and even many years seasoned drivers do that.
It is always good to have a spotter as there are places on that RV you simply can't see, and need someone back there to check on things for you. I signal like Jenny does. I stand where I can see Milt in the mirrors. If I can't see him, he can't , see me. I also signal slowly as the mirror he is looking in is small. I move my left hand to the left and my right hand to the right to designate movements in those directions... Both hands held up mean come straight back. A hand up with palm facing him means Stop. Often, I have him stop so I can walk to the other side of the trailer to check out how we are doing. If I throw things on the ground and fall down and kick my feet that means we have messed up bad!! Grin.
Hang in there. Y'all will get your routine down pat with practice.
Happy Travels!
Joella