Anyone with Manager or Admin access can add users. There is no additional cost or limit on adding users to your account.
First, navigate to Settings > Users.
Enter the user's name and email address, and select a level of access.
Contributor: Contributors can only connect their own inbox in Settings, and can only see the replies in the inbox that pertain to their connected inbox. They have no other permissions to view or edit.
User: Users can view everything and export data. They cannot view, create or edit skills, manage users, manage integrations (MAP, inboxes, subdomain), ignore domains, or access the data privacy feature.
Manager: Managers have access to create, edit, and manage across all functions in the account (including users and integrations). They cannot access the Subscription tab in Settings to view billing information.
Admin: Full access to all functions in the account.