ortho tri cyclen lo

Hello my name is Maria, I am a young teenager. I didn't get on the pill for a birth control and I have a few questions I didn't ask my doctor when she prescribed it. First I'd like to say that I have had irregular periods I've only had about 6 since I turned 13. I haven't had my period for about 10 months, which I didn't really go to the doctor for because I just generally forget that I have woman tendencies. I have moderate/severe acne, 149 lbs, and 5' 2". Anyways I start tomorrow on the pill and I wanted to ask how to take them and when should I expect my 'period'?