If you have been given a community's password but were not properly given maintainership and are unable to see the community at http://www.livejournal.com/community/manage.bml, you can grant yourself maintainership by using the following page: http://www.livejournal.com/community/transfer.bml
2) How do I add users and grant posting access to my community? needs help.
Last paragraph to:
If you've selected to create a closed community, no one is able to request membership. To add someone, you will need to invite them. You can do this by entering their username in a blank box at the bottom of the "Members" page. When you have entered their username, select the appropriate permissions you would like to grant them.
If you enter incorrect permissions, you can change them by re-entering the username and selecting the correct permissions. Invitations that you or another maintainer have sent, as well as the status of those invitations, can be viewed with the "Invitations" link.
Or, instead of the above, we can just have a new invitation FAQ and throw a link into 80. I'm leaning on a new FAQ (gah, kill me) having info about invites, how to send them, how to accept them (rather than adding info about accepting them to "how do i join..."), etc (since emails are no longer in use). I'm totally lacking in wording proposal, though. :/
Erm... I think that was it for now. Stuff about new community creation method coming later.