Just ordered OPK. Now what?

Khesa • Loving my hubby <3
Went on amazon and ordered a 30 strip pack of ovulation test strips. Not sure if I test every single day as soon as they arrive.. Or do I start after a certain day? My AF is here now, 13-17 and I should have my OPKs by 4/18. According to glow my "fertile window"  begins 4/19 (25 day cycle). So what should I do?
​This is our first month TTC (4 months after MC).