First remove existing members:
  1. onCampus > Procedure > Community > Community Group Pages.
  2. Edit the group.
  3. Click on the Roster tab.
  4. Click Manage.
  5. Remove the members.
Then, change the group's membership:
  1. onCampus > Procedure > Community > Add/Edit Community Groups
  2. Edit the group.
  3. In the Membership drop down, select the new membership.
  4. Save & Exit.
Then, go back to the community group's roster and add the members back in.
  1. onCampus > Procedure > Community > Community Group Pages.
  2. Edit the group.
  3. Click on the Roster tab.
  4. Click Manage.
  5. Add the members.