To change the membership of your team, go to the team page and click ‘Members’. The members of a team can be managed in the same way as the members of a discussion: see Inviting Participants to a Discussion, Inviting Participants by Email Link, and Participant Rights and Roles.
Note that for teams, the equivalent of the Editor role is Member. There is no Viewer or Writer role. This should be distinguished from the roles teams are granted in individual discussions - teams can be given any participant role, and the role given to a team will accrue to all of its members. Roles within a team simply control what rights members have in regard to the team itself.