First, if your pool is a swamp, just drain it, clean and refill it. Its more cost effective.

If your pool is green and cloudy then here is what you do.
 

• 1. Buy a 50# bucket Calcium Hypochlorite from Costco or Sam's.  (Don't bother going to Home Despot.) It will cost you about 120 bucks. Use 1 # to 1.5# per 1000 gal. If you have a plaster pool and  really want clear your pool fast then you'll need to find your local wholsale pool supply warehouse or wherever us pool guys go and buy a 25# bucky of a little something called (Trichloro-s-triazinetrione) Better known as Super Algae Destroyer by Omni. Do not use this if you have a Vinyl or Tile Pool. This is the same type of chlorine as your tabs but in granular form. Use 1/2# to 1# per 1000 gallons. What ever you do don't bother with the Dichloro-s-triazinetrione which often come in small 1# packets with promises it can't keep. Yes my children,  that is correct there are different types of chlorine for different applications.  Listen!  Listen carefully!

You will also need a 32oz. bottle of liquid Floc or as its often referred to as Drop-n-Vac.  Careful!! read the directions carefully.  You cannot get this stuff in your filter.

• 2.  First Skim or vacuum out as much debris as possible from the bottom of your pool.  You don't have to get it all.  This will make it easier.  Add the appropriate amount of Calcium Hypochlorite or Trichloro as directed above broadcasting it evenly across the whole pool. Then brush all surfaces, even the bottom.  Stir it all up good.  Then add the Drop n Vac liquid floc being careful to fallow the directions on the bottle.  
• 3. Leave pool off overnight and let it all settle out.  In 24 to 48 hours the pool should be crystal clear with a light yellow film on the bottom.  Carefully vacuum out to WASTE.  NOT THROUGH THE FILTER.  If you don't know how call your local pool guy.
  

Note:  I read another guide by some blonde who drank far to much expensive wine.  She suggested adding tabs to the "skimmer thingy".  NEVER ADD TABS TO YOUR POOL VIA YOUR SKIMMER.  TRICHLOR  IS VERY ACIDIC AND IT WILL DRY OUT YOUR PVC PLUMBING, MAKING IT VERY BRITTLE ,AS WELL AS EAT OUT THE CERAMIC SHAFT SEAL IN YOUR PUMP. 

Aloha