Many above-ground pools' directions say you can set the pool up anywhere. However, there is usually much more to it than that. Sadly, many people do not discover the importance of levelling the ground beneath the pool before it is too late. A difference of more than 2 inches anywhere on the pool can cause serious damage. There's a temporary fix to an unlevel pool, and a second method is more permanent.
Measure four to six points around the sides of the pool to find its lowest area, using a measuring tape. The water level should never be more than 2 inches different all the way around the pool.
Scoop some dirt with a shovel and start to build it up under the lowest parts of the pool. Place a 2-by-4 board across the ground to hold the dirt in place. Use pavers to hold the boards upright against the pool walls.
Wet the dirt with a hose to pack it down. This method should only be used if it is impossible to drain the pool. It is a temporary measure at best, and will not hold forever.
Drain the pool with a swimming pool pump. Drain the water into the city sewage lines. This will take several hours. It is OK to leave an inch or two of water in the bottom of the pool.
Move the pool to another location in the yard. If you have to collapse the pool, do so. Otherwise, just shift it out of the way.
Drag a long 2-by-4 board across the ground to find the lowest spot. The lowest area will show up as a depression under the board.
Lower the surrounding soil to the lowest level of ground with the shovel. Raising low spots is much harder than lowering high spots. Use the tamp to press the dirt into the ground tightly after shifting. Check the level of the soil again with the level, and make any necessary adjustments.
Pour 1 to 2 inches of sand over the top of the soil. Spread with a rake and then with the 2-by-4 board. Replace the pool over this area and fill once more. The pool will now be level.