When to use ovulation tests?

So I’ve been ttc for 6/7 months now. My cycles started acting weird about 7 months ago, it was always pretty regular but all of a sudden my periods would come 2 weeks later than it should’ve had. Now my periods are kind of on schedule.

My earliest cycle that I tracked on my app was 38 days, and the shortest cycle that I tracked was 30 days. So my cycles varies between 30-38 days.

Now my question is when to test to see if i’m having my ovulation? I don’t exactly know about when my ovulation is. And how many timer should I test? And for how long?

Sorry if this is confusing, I’m not really good with words and English isn’t my first language.