This is unfortunately not a RTFM. RedHat did not enable menu editing, because of buggy gnome code.
RTFM: http://www.gnome.org/learn/. Start with the User's Guide, then dig into the Desktop System Administrator's Guide.
See: http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=81215
There is a way to get it enabled, but that seems to be risky See: http://www.redhat.com/archives/fedora-test-list/2003-October/msg03800.html
Can somebody of RedHat inform us if there is any change that this will get fixed (or do we have to wait for gnome 2.6) It's a pretty frustrating bug.