Place your kickstart file on the NFS server. NFS share must - of course - be readable by the server you want to install.
Boot on Red Hat ISO image.
Press esc key to return to boot: prompt
enter the NFS server IP and path to kickstart file
boot: linux ks=nfs:<ip of NFS server>:/<path>/<kickstart file name> hostname=<hostname>
Press enter and enjoy installation of Red Hat server