When should you start taking OPKs?

I’m TTC baby number 2, this is our first month actively trying. I got off of birth control in September 2019, and we’ve been just not trying not preventing since then, but we’ve decided to start actively trying. We used OPKs every single cycle when we were TTC our first, but it’s been so long since then that I don’t even remember when in your cycle you’re supposed to start taking them 😅 I attached a picture of my last few cycles. I started my period this month on 4/20. If anyone could give me some pointers I’d really appreciate it. My cycles since having my son have been so crazy and different in length that I don’t even know where to begin 😅 this period and my last did start on the days glow predicted so I think I’m finally starting to regulate back out, before I had my son my cycles were always 29 days on the dot.