The easiest and best way to fill an above-ground pool is with your garden hose. When the installation is complete, simply grab a hose and start filling the pool. You should control the filling process because the pressure will build up as more water gets inside (especially if you have an above ground rectangular pool).
If the walls seem to bulge or creak in any way, we suggest turning off the water and double-checking if the pool was set up correctly. Once the pool is completely filled with water, it’s hard to adjust or reposition its pieces and parts. It’s much better to do it right the first time than to fix it halfway through.