How do you know an ovulation test is positive?

My husband and I have been trying for two years. I finally got in to see a doctor and found out it was my insulin levels. So my doctor put me on metformin and I started my period 4 days later (after not having one for like 2 months haha) and he put me on Clomid on day 3 of my cycle. So I’m going to start taking ovulation tests and I’m not sure how to tell if it’s positive or not? Is there a good app to use? I’m on cycle day 9. Is now a good day to start taking them?