Installing an RV cover is pretty simple with the right technique. First, you should wash your RV and make sure it is clean and there is no debris such as leaves or pine needles on the roof. This not only helps to protect the finish, but it also ensures your RV will be clean when you uncover it again. Once it is dry, place the rolled up cover at the rear of the RV. Most covers come with a rope--use this to pull the cover up on top of the RV. If it didn't come with one, you can always just tie one to it. Some find it easier to fasten the rope to their belt loop and pull the cover up while they climb up on to the roof. As you pull it up, the cover should start unrolling. Then, once you are on the roof, spread the cover along the length of the RV. Then, unroll the cover down over the sides of the RV and secure them with the attached straps. Tighten the cover as much as possible to remove all of the slack so that the cover doesn't move much in the wind.
Here is a short video demonstration that may help: