Ovulation test help!!

Cari

I really don’t know when to start testing it’s so confusing. I started my period Nov 12 and it ends Nov 18. My cycle this month will be around 33 cycle days. Clear blues instructions it says to start testing on the day showing under your cycle length which under 33 cycle it shows 13. So would I count from first day of my period up to 13 days and that’s when I should start testing?