Hi Sharon, welcome to the Planted Tank, the best place to battle green water!
There are a few options here, and I will try to mention disadvantages of each one.
1) Do nothing. Sometimes GW will disappear by itself, because it is eating up that specific nutrient combination that it requires. For this to work, you should discontinue water changes for 8 to 10 days, everything else can continue as usual. Disadvantage: This works great with tanks that are new, and in the process to establish their balance. For other tanks, sometimes this doesn't work. Also, it takes some patience, and the first days the GW actually can get thicker.
2) Blackout. Cover the tank for 4 days. Before and after you need to do water changes, because the dying GW organisms possibly increase NH4 levels, while plants -- in the dark -- won't be helping much to take them up. Disadvantage: This doesn't battle the source of the problem, so a week after you uncover the tank you might be greeted by pea soup again.
3) UV sterilizer. Works great to kill them. Need to keep an eye on NH4 levels, do water changes, clean filters, etc to avoid buildup of dead matter. Disadvantage: costs some money, and since we are fighting the results of some imbalance, we need to repeat treatment as necessary, or let it run all the time.
4) Diatom filtration. Diatomaceous earth contains tiny little shells of tiny little critters. Send dirty water through it, all the dirt, including GW, remains stuck in the diatoms. Disadvantage: Costs some money, can get a little messy if you are not careful, and might need repeated treatment.
5) Daphnias and other little crustaceans live off GW. Problem is that in the food chain, fish live off Daphnias, so you'd need to separate the two somehow. Disadvantage: I have never heard that this actually worked. It would be great to have a second tank full of daphnia which clean the water of your show tank, and once in a while you scoop some of the little critters over to feed your fish.
That should get you started!