Still confused about when to BD... WHAT AM I DOING?!

Mary • 36 y/o due 🌈Feb-07-2021 🌈 5 years TTC & 1 MC in 2018.
So, if the sperm live a few days inside a woman's body, what should be the target date (in relation to evidence of EWCM & OPK testing positive) that we have sex?? Whenever I'm feeling frisky? When my CM changes? As soon as I see 2 bold red lines? How long after the surge is detected will the egg wait around for his swimmers to complete their mission? Aaaaaugh!!