You have to put the kickstart file somewhere where the installation can see it. For instance, at work we use NFS. So, I put it in an NFS directory.
Then, when booting the install CD at the prompt I type
linux ks=nfs:10.0.69.69:/tmp/ks.cfg ksdevice=eth1 ip=dhcp
Or something similar. In other words
ks is for kickstart
I'm using NFS so I indicate that, as well as the location of the file
I'm using eth1 on the machine that I'm booting--that is, the one on which I'm going to install, so that's the eth1 part. If I were giving it an address, it might be something a bit different like
ip=10.0.69.70 netmask=255.255.0.0 gateway=10.0.0.1 dns=10.0.100.243 text
So, that's one less advanced way to start it. The other way to start it, which is more advanced and bit more complicated, is to boot the computer from the network and have a tftp server holding the file. I haven't done that in a long time, so I don't want to give you wrong advice. Just google, or search the forums for something like kickstart pxe and you should find information on doing it that way.