to start with get a BBT themometer and a chart. There is some good ones online just search for free online BBT charts. pick a time and stick to it the same time 7 days a week.Start the first day on AF.The first thing you do when you wake up is temp no talking nothing. You have to have atleast 3-5hrs undisturbed sleep for it to be correct. I kept two charts the one online and one by my bed so I could write it down and go back to sleep and not forget what it was. In a few months you will see a pattern of your pre O temps and after O temps. before you O your temps will stay kinda low you might have a spike and then dip the day before you O or the day of then your temps will be higher .4 degrees for 3 days in a row shows you did O. your temp will remain up until time for AF some womens temp will start going down before AF and others will stay high and start going down after AF shows. After you O you will cound DPO's (days past ovulation) this will be your luteral phase and most womens is 14 days long.16 days of high temps could indicate pregnacy.
I hope this isn't to confusing if you need more help just ask and I will try to explain. it just takes time and you will be able to tell if you O'ed or not and when it was. I learned alot about my body.
Hope this helps
Tami