hi, we don't cover our pool in the winter, so usually have a dark green swamp every spring. To start, hook up all the hoses, pump & filter making sure there are no leaks. Then fill your pool half way up the skimmer. Once everything works, you will need to add shock. This is available at your pool supply store. We usually add shock & a chlorine stabilizer at the same time so the shock doesn't wear off so quickly. Within 24 hours the color will usually start to lighten. Take a brush and scrub all the sides and bottom to loosen the dead/dying algae. Then vacuum, vacuum vacuum. Once the water looks cleaner (you still won't be able to see the bottom) you need to take a sample to your pool supply store to have it analyzed. They will tell you what chemicals to add, etc. This usually clears up any cloudiness left over. All in all, it usually takes us about a week to get it going from green. Good luck!