Can't find "Add User" option in Zoho One Mail control panel

Can't find "Add User" option in Zoho One Mail control panel

Hi, I am currently in tryout period for the Zoho One suite. For the time being I am the sole user, but I intend to manage 3 domains under it, alzamon.com, naranjactiva.design and naranjactiva.com. Only alzamon.com is currently using Zoho Mail, but I'd want to add some more accounts/aliases under naranjactiva.design. However I can no longer find any "Add User" options on the Control Panel. Something wrong?