Answer:
Search the question 'How do you get magic'. It's the same reply I'd give for either.
A Pagan Perspective
As a practicing pagan/witch I can only tell you how it happened for me (and some of the members of my group). I started young, watching and learning from nature, my shaman, my family members, and eventually expanded my study to a personal library of over 500 books, and still growing (some very old, some hand written, and some very newly published). As my abilities increased I found others of like mind and shared knowledge and experiences. Once I started researching, creating, writing and performing my own rites, rituals and spells. I found a "calling" to start a Circle of my own. Not all practitioner become members or leaders of Circles/Covens but all of them retain a life long need to continue their "magical education".