1. The User management is handled from the Settings tab on the left hand side management panel.
2. After going to the Settings page choose User management. Here you can view your organization structure, find a list of the users in your organization and also invite users to teams (more info on that here).
3. By clicking on one the users name you can view what rights that user has (admin, editor, viewer). You can read more about the user rights here.
4. You can change the role by choosing which the new role should be and then clicking Save.
5. You can also Remove a user from your team by clicking on the Remove from team tab.