Question (Maybe TMI)

Tanya • Miscarried at 8 weeks 2/12/18.. 💔👼 🌈 baby.. 11/30/2018
I'm curious to know what the whole fertile days means. Is it basically saying to have as much intercourse as possible so that the day you ovulate you have a higher chance of becoming pregnant? Also how do you know if you are actually ovulating? This is all son confusing and frustrating. I always assumed you just find your partner and have your baby. Boy was I wrong. Its been two and a half years of hoping and trying already. Also has anyone tried the preseed? At what stage do you use it?