I have a 16' x 48" round intex ultra frame pool. It seemed to be pretty level to me when I put it up. However when I filled it up with water, one side had about 5 or 6 inches more water than the other side. It is clearly not level. How should I go about fixing this problem? I know I will probably have to take the pool down and start over. What is the easiest way to solve this problem?

There is no easy way to level your yard. Try renting a water level so you can shoot a grade at least 16". Dig down to get a flat surface, do not try to build up. How to build-install above ground pool