Yes, you will have to MAINTAIN a "shock level" of chlorine in your pool for as long as it takes to clear your pool.

Please read this thread for how you can get started with this process.

Current pool balance numbers are important. If you don't have a Taylor K-2006, please order one. While you await it's arrival, go to your local Wal-mart and pick up the HTH 6-way test kit. Once you have a kit in hand, post your numbers here.

Here is a guide for how high you will need to maintain your chlorine levels while you clear your pool of algae.

You will also need to be running your pump 24/7 to help clear the pool, along with daily brushing.

If I have forgotten anything here, I'm sure others will pop in to help.