Only council members or higher can post spells to a coven spellbook. However, you can post it in Spells forum, if you wish to share it with others. As far as I know, you can't keep a personal book for spells here on the site.
If you wish to contribute spells for the site, you have few options that you can choose in order to contribute the spells you want :
1. Join the coven " Spell Casters" -
Spell casters is a coven which is open for all of the members of the site. Everyone who joins the coven becomes automatically a council member, which is the minimal position you need to get in order to contribute your spells for the site. So you can simply apply to join Spell Casters ( your application will be immediately auto accepted to the coven since the coven is open to everyone who wishes to join it ) and then contribute the spells by using your auto council position.
Here's a link to the coven Spell casters :
2. Join a regular coven and have a concil member position or a higher one (such as the priest or the priestess of the coven) -
Coven Council members and members with higher positions (the coven leaders) are the only people who are able to contribute spells for the site by using their coven's spell book editorship options (same thing with adding articles to the coven's spell book).
So just join any coven you like, prove yourself as a member who deserves the council postition or a higher position ( contribute coven posts , participate in the coven chat , help members, etc ). After you prove yourself as a member who deserves to be promoted in your coven, you'll get the council position or a higher one, and then you will be able to contribute spells and articles to the coven's spell book by using the coven's editorship options.
Here is a link to all of the active online covens of the site :
3. Ask from the council members or from the coven leaders to post the spells you wish to contribute for the site -
As I said, Coven Council members and members with higher positions (the coven leaders) are the only people who are able to contribute spells for the site by using their coven's spell book editorship options (same thing with adding articles to the coven's spell book).
So if you do not have the ability to prove yourself as one who deserves a council position or a higher position, it's alright.
Simply send the spell you wish to contribute for the site to one of the council members or the coven leaders, and if they'll find your material as qualified enough to be posted - they might contribute the spell / article or anything you wish to contribute for the site for you. But remember that from time to time you might be rejected if the coven leadership doesn't like the spell or find it as qualified enough. Your spell has to be always very qualified to get the permission to be contributed by members with higher positions in order to keep the coven spell book clean, organized and qualified ! Of course that they will have to give you the credit for creating the contributed material, if you were the one who has written it.
4. Post your spell in " Spell Suggestions " forum -
Spell Suggestions is a forum in where you can freely post your spells ( unless they are not real magick spells and considered as fluffy / fantasy spells).
You can suggest spells you know freely, by opening a new thread and there pasting the spell you wish to contribute.
This is a very good solution and option for someone who wishes to contribute spells for the site and doesn't really have too many options. It is simple, comfortable and totally free !