Ovulation tests

Kaley
Hi, I'm new to this app, but am excited to see the results. I've used "period" apps before, but none of them had a forum like this...
Anyways, my fiancé and I have been trying for almost 2 years. I do have a child, so he is thinking it's him. We are getting married 7/31/15 but have wanted to have a baby for awhile now. 
Can anyone tell me about ovulation tests? How they work? What do they do? Any advice to help. 
Thank you!