You must be an administrator.
Sugar automatically assigns every user to the Global team and to the user’s private team. Additionally, you can assign a user to other teams. The Global team is a universal team to which all users belong. Every user can view records that are assigned to the Global team. Users also belong to their own private team in order to view and manage their assigned records. Private teams include the reporting hierarchy. Hence, users can see the records of any user who is below them in the hierarchy, regardless of their team membership. For more information on managing teams, please refer to the Team Management documentation.