After you create the group, you can invite members by clicking on "Manage Members."
![Image of Manage Members in Zotero Online](//libapps.s3.amazonaws.com/accounts/202817/images/manage_members.png)
Once in "Manage Members" you can "Send More Invitations" and/or "Update Roles of other members.
![Image of Update Roles in Zotero Online](//libapps.s3.amazonaws.com/accounts/202817/images/Inviting_Members.JPG)
You add members by using the email address they signed up for Zotero with. Library/Group members will receive an email from do-not-reply@zotero.org
Once members join the group, they will need to sync their Zotero accounts before they see the group in their Zotero library.