@ kylekat you can join any coven starting from day one. each coven deals with different things and has different requirements. some you just click 'join' others you need a picture, a bio, and you have to fill out a questionnaire to be approved or denied.
@Fairyprince it's been stated already how, but you'll have to wait a while after putting your name in. i requested to become the leader of an inactive coven over a month ago, so just be patient. i think only Pet, or admin can choose, so it'll be a while. if you want to join a coven to teach, join Spellcaster, they automatically put you in their council so you can add spells and articles.