About inviting users
As an administrator, you invite users to join your organization. As part of the invitation process, you can preestablish logins for users, or you can have users log in with existing logins or create new ones. You can send invitations one at a time, or you can upload a file and send invitations in bulk. Potential members receive an email invitation with instructions on how to join the organization.
The total number of users your organization can have is based on the subscription your organization has purchased. The Status page shows the current and remaining number of members in your organization. For more information, see Viewing subscription status.
If your organization is testing Enterprise Logins (beta), during the initial beta release the only option is for users to join automatically once you have set up the federation. In the final release, you will be able to restrict membership to only those users who you explicitly invite into the ArcGIS Online organization. For more information on Enterprise Logins (beta), see Configuring security settings.