When there's dirt and debris in the bottom of the pool you can use a vacuum to suck it to the pump basket and filter.
Items Needed:
1. Extension Pole
2. Vacuum Head
3. Vacuum Hose
How To:
1. Stretch the hose out so its completely flat on the deck.
2. With the vacuum head attached to the pole, attach the swiveled end of the hose to the head.
3. Lower the vacuum down the side of the pool and then guide the hose along the wall to fill it with water. Once you get to the end of hose it should over flow with water.
4. Pull the hose through the skimmer and plug it into the suction line.
5. If your suction isn't very strong you can close some of the other valves that you aren't pulling from. Listen to the pump and watch the water flow to ensure you have enough flow still going to the pump. If the suction is too strong, your vacuum head might stick on the bottom of the pool or the hose might colapse.
Now you're ready to vacuum! Go slowly around dirt to not stir it up and make sure to check your filter gauge afterwards to see if you need to backwash or rinse out your filters. If there was a lot of debris you'll have to clean out the pump basket as well.