Basic use of group permissions on Redhat Enterprise Linux v4

/etc/group is a file that contains the groups and users that belong to that group. You can append ,username to the end of each group line to add another member to that group.

Syntax to make a file or directory belong to a group:
chown :group FileOrDirectory

Command to give permissions to a group:
chmod g+rwxs FileOrDirectory

(omit r to leave out read, w for write, x for execute s for sticky bit) The sticky bit is used to give all newly created files below that directory the same permissions.

I don't yet know how to recursively give all existing files below the directory the same permissions.