I don't know how to use this thing!!!

Ok so hopefully someone can help. I stopped my bc for the first time in 13 years Monday. I was on seasonique so only got AF every 4 months. So... When trying to log I have no clue what my average cycle is and that is not an option! My period started today but the app already logged for tomorrow. How do I chart if I don't know answers? Will that mess up my ovulation accuracy?