For a normal CD-ROM install, you boot the system with the RHC Linux CD-ROM inserted in the CD-ROM drive. If you wish to install over a network, you will need to mount the RHC Linux CD-ROM on a machine that supports ISO-9660 file systems with Rock Ridge extensions, and NFS. Export the CD-ROM file system via NFS.
You will use the same boot and root disks to do a network install, and you will need to know the NFS server's IP address and the path to the exported CD-ROM.