You must join a coven and be promoted to council. If you just Spell Casters you will be automatically promoted to council. However, you can join any coven and many will have a coven forum where you can submit spells and a council member or the high priest/priestess can submit it for you. Most will ask you spell check your work, make sure it is not fluffy, and ask you to pick catagories for it to go into. They will credit the work to you at the bottom of the submitted spell from what I have seen.