Boot the to-be-installed machine off your RedHat boot floppy as usual, but instead of pressing RETURN at the SYSLINUX prompt, type linux ks.
If you're lucky, this will be all you have to type!
If you customised your RedHat boot floppy as outlined above, you won't even need to do this bit :-)
Since we're really just automating the normal steps involved in a RedHat installation, the normal dialogs may appear if/when KickStart gets confused about what to do next. The most likely case is that your network interface won't be detected automatically, and you'll be prompted for its IRQ and I/O address space. KickStart tends to need help for ISA bus cards, but detects PCI bus cards automatically.
You can keep an eye on what KickStart is doing by by switching virtual consoles as usual: