Ovulation Testing

Jessica
I stopped taking birth control about 9 months ago and we have been casually trying since then. I don't use opk's or take my temperature, we really just try to BD during what the app says is my fertile window. 
I have opk's and I would like to start using them. I've read different things about when the best time to use them is. I thought it was better mid afternoon, although a close friend of mine did it first thing in the morning and was successful with that.
Any insight would be appreciated!