Hey there!
I'd recommend reading 'Taking Charge of your Fertility' as the girls above have mentioned. I think you can buy it on Amazon and it's the 10th version you are after.
Check here:
Amazon.com: Taking Charge of Your Fertility, 10th Anniversary Edition: The Definitive Guide to Natural Birth Control, Pregnancy Achievement, and Reproductive Health (9780060881900): Toni Weschler: Books
I read that from cover to cover, then contacted a fertility place in New Zealand who did correspondence courses via email/phone and mail. My instructor gave me one thing to do each month, and built on that over the following four months (ie first month: take temperatures every morning, second month: take temps and write down what cervical fluid I was feeling/seeing each day, third month: then take temps, check cervical fluid and check cervical position every day and so on).
I 'charted' for 4 months with my instructor who got me to send my charts to her every month to see how I was going and to make sure I was using the 'rules' correctly as I was using charting to avoid pregnancy for the first 18 month or so.
I would recommend doing a course if you can. I did try using the website 'Fertility Friend' for a while, however it kept telling me I wasn't ovulating. My instructor showed me that my ovulation 'signs' where much more subtle than what was normal, but that I was still ovulating ('Fertility Friend' even told me I wasn't ovulating AFTER I fell pregnant!!).
I personally think it's much easier to chart on paper, so you can get your head around it all before you start using something like the 'Fertility Friend' website, as you need to trust your own instincts and signs your body is giving you rather than what a computer is telling you, if that makes sense!
Maybe post on the 'Natural Family Planning and FAM' (Under 'Women and Family Health') as well, as I know the host there will be able to recommend where you could do a course.
Good luck!