Dpo Question

Bri • 23 ❤️ ❤️ Dog Mom ❤️ ❤️Expecting Baby #1 12/14❤️❤️ soon to be divorcee 🤷🏾‍♀️

How do you count Dpo? I’m using OPKs and idk how to exactly count it. Or if I’m doing it correctly.