How to modify the list of groups the user belongs to?

A user can belong to more than one group. How create a group you can find on section Section 4.11. The list Other groups displays a collection of existing groups (see Figure 4.8-1).
From the Edit User page, select groups (single or multi selection - multi selection can be done by SHIFT or CTRL key) from the Other groups list, you want the user to be a member of.

Figure 4.8-1 : Change user groups.

To remove the user from the groups is a member of, select from the Edit User page, the Blank item from the Other groups .

Figure 4.8-2 : Delete user from group.