Clarifier wasn't needed and didn't cause your green pool.
The cause of a green pool is too little chlorine for too long. Even when you get an "OK" reading from your testing, it usually isn't enough chlorine to keep the pool sanitary & algae free.
Please fill out your signature with the pool details so that we can give you personalized advice. Pool type, equipment description, etc.
It all starts with testing. You need to get a good test kit that can measure pH, FC, CC, TA, CH, and CYA. I recommend the TF-100 from TFTestkits. Don't let sticker shock set in. I've never seen anyone that has regretted getting the kit. Test strips and pool store testing are inaccurate.
Lots of abbreviations and these can be read about in Pool School. Start by reading the ABCs of Pool Water Chemistry and take some time to read through Pool School.
Most important is to get chlorine in the water. While you are waiting for the test kit to be delivered, you can add enough liquid chlorine to get FC to 5ppm. That's regular bleach from your favorite grocery store. Non-scented, not splashless, not Chlorox brand. And continue to brush daily. Add this each day until you can test for the chlorine. You need to follow the FC/CYA Chart for your chlorine level.
Start there for now. Once you get your kit, run a full set of tests and post them here and we can offer more advice.
Please ask about any questions or issues you are having and you will get some help.