The best way to learn NFP is from a qualified instructor; one who is certified by an NFP teacher training program. For more information about NFP instruction available in your community, contact one of the following organizations:
World Organization of the Ovulation Method (Billings): https://woomb.ca/
Napro Technology: https://www.fertilitycare.org (see Canada)
*Books describing the NFP methods taught by these organizations are available from One More Soul in our online store.