Trying OPKs

Alex • Married to my best friend and the love of my life -- my Airman. Michigan born and raised. TTC #1!
Hello, ladies! I've decided to try some OPKs this month, since I've been having trouble tracking my ovulation on my own. I'm wondering though, when did you ladies who have use them start? Right after your period ended? Or did you wait a couple days? There aren't many that come in a pack. TIA!