Help with opk- first time

Caitlin • 1st born May 2017, 2nd born May 2020, 3rd due May 2024 💗

I started my period today so I’m sad but excited to try again this month using opk’s for the first time. I just ordered pre seed and the clear blue digital opk kit on amazon. My question is when do I start testing? Right after my period ends?? Any other tips??? This is month #3 trying for baby #2

Thanks in advance!