You can edit the groups of which a user is a member through the user list.
Changing a User's Group Memberships
1.Click User in the menu bar.
2.The list of users is displayed. The groups column lists the user's current group memberships.
3.Scroll the list to the user who you want to edit and double click on the row.
4.Click on the field in the groups column. The drop-down list allows you to select which groups the user is a member of.
5.Set the user's group memberships and click Save.