Your onot perishah are calculated as outlined in the articles on the site – the same Hebrew date, the interval between the last two periods, and day 30. On each of these days you observe the onah (daytime or night-time) corresponding to the beginning of your last period. Our article How to Keep a Calendar should help you get started.
Keep track for a number of months of your exact interval. If you have 3 consecutive intervals of 32 days or more more, then, according to the posek of our site, you are exempt from observing yom hachodesh and onah beinonit, until you have a shorter cycle.
On each onat perishah you need to abstain from relations and do at least one bedikah. Please read the articles on the site for a detailed presentation of this topic, and feel free to get back to us with additional questions.