First timer please help!

Emma • 30 years old. Chef. Married
My husband and I have been trying to have a baby for about a year or so without tracking anything. So yesterday we decided to try tracking ovulation and bought a clear blue easy ovulation tester. I am currently on my period and glow says my window for ovulation starts on the 28 should I start testing on that day or should I start right after my period? I'm so confused.