Go to Administer and select Groups.

Find the group in the list, and select Manage on its row to open the group's page.

In the Members section, select Add members. The Add members dialog opens.

Note: The Pending group has no Add members button. A user sits in Pending until they are given a group, and is moved out automatically when they are.

Search for each person by name or email address, and select the check box beside them. People who are already members, and deactivated users, are left out of the list.

Note: A person can belong to several groups at once. What their groups grant is combined, and the most permissive result wins. The exception is a direct deny, which can name a group. Adding someone to a group that is denied a permission on an entity removes that permission there, unless a direct grant restores it. Denies never apply to members of the Administrators group.

Select Add members.