For Community Admins
After successful login, click Community -> Manage Communities
If you have been added as a community admin by another community admin, you can see the communities with admin access on this page. You can also create a new community yourself.
When you enter the community you will see an Edit button, which you can use to edit the community information.
You can also click on the Members page to add/approve membership applications.
If you choose to add a member directly, you need to know the person's username. If you are a community administrator, you will see the Approve and Decline buttons to decide whether or not to allow members to join the community.