Just opened pool, its green, whats my first steps?

Use these tried and true steps over several days. (1) Clear as much large debris from the water. Stirring up the sediment is okay: it will settle in a few hours. Do not vacuum the pool, as this can clog lines and equipment. (2) Ensure the water chemistry balanced or the water will never clear up. (a) Adjust pH and alkalinity, (b) chlorine shock the pool repeatedly approximately every 8 hours until the water begins to clear, and (c) use an algaecide. (3) Run your pump constantly until the problem is clear – not almost cleared up. You must run it 24 hrs a day until you are sure there is absolutely no more algae or sediment. (4) Backwash your filter often: every 4 hours or more. You can not over backwash, but if you don’t do it enough, you risk clogging or burning out your pump. *note: a diatomaceous earth filter will clear up a green pool faster, but remember to add new d.e. after each backwash. (5) After the water clears up, there will be debris on the pool floor. Depending on how much there is, you can vacuum it yourself or have it professionally power vacuumed to avoid a chance of over-working your system. If the problem persists past 5 days, it’s time to call in some help. Although unlikely, if you have resistant black algae these steps will not work, and more drastic agents must be applied.

First, clean the filter. Fill the pool. Put in algaecide that works on the type of algae you have. (Consult a pool supply store.) The instructions will tell you to then put in shock/chlorine. Now start brushing and vacuuming. It's hard work but the stuff will go away. Clean the filter again. Once a week check the chemical balance (or take a sample to the pool store and let them check it) and add a no-phosphate additive to keep the algae from coming back.