Temp to predict ovulation.

I just bought a thermometer yesterday. I'm also started my period yesterday, but I want to start using this method to predict ovulation since the test are expensive. However, I'm confused by the ovulation chart that came with the thermometer. It says your temperature will drop in the period following ovulation and that is the best time to conceive. I just read a post on here though that said when you temperature goes up you are ovulating. I'm a little confused. Does it mean when temp drops start having sex because a temp spike is to follow which is when you ovulate?