Account owners and admins have the power to invite new users to Groove. To invite a new user, go into your account Settings > Company > Users and click the + Add User button in the left sidebar. 

Fill in your new user's name and email address, and select whether they're a regular agent or an admin.

Once you click Done, we'll send your new user an invite to complete the account creation process.

Please note that adding a user does not automatically start forwarding their mail to your Groove account. Users and mailboxes are separate things and you can read more about getting started with your mailbox here.