For every domain in opentaps CRM2, there is an administrator with special permissions to administer the users and emails. When this administrator logs in, there will be a small cog in the upper right hand corner which has options for Users and Emails:
In the Users screen, you can create new users:
or search and update existing users:
Here you can manage the contacts profile as well as the security permissions of your users.
Note that users are contacts with user logins, but these screen treat them as one. If you want to see your users as contacts, including their activities history, go to the Contacts tab and search for them by name.
Additional configurations can be performed via the REST administrative API. See CRM-2 Administrative API.