Leveling land with a roto tiller for a 14 ft pool.

[ahutchins9]

Ok So we bought our kids a pool this past weekend put it up filled it with water and of course its not level. Neither me and my husband know anything about leveling land so I did some research and found it would be easiest to do with a roto tiller. My questions is should i till up the entire area the pool is on or just till the higher area and remove the dirt to match the lower area? Like I said we have no idea what we are doing. The ground is level half the width of the pool. Once we got it filled there was a 3 inch water difference from the left side to the right side. The right side being the lowest. So if i tilled up the left side and removed 3 inches of dirt then spread it going towards the right side would that work? Thanks