I'm not sure about redhat, but in Slackware, the startup scripts are located in /etc/rc.d There might be something similar in redhat, perhaps /etc/rc.d/init.d/.. blah blah. I'm sure there's some GUI in redhat that does system configuration for you.
To check if it works, open a shell with root privileges. Connect the drive up, power it on, stick in a disk. At the shell prompt, type in, 'modprobe ppa' Some messages should go scrolling up. If that works, you can try mounting the disk. Make a temporary directory, say /mnt/zipdrive Then, to mount it, type 'mount -t vfat /dev/sda4 /mnt/zipdrive' If something is on the disk, you should be able to see it now with 'ls /mnt/zipdrive'
If that doesn't work, then you'll have to compile a kernel with generic scsi support and the ppa module (another topic far far far beyond getting a zip drive up and running), but I'm fairly certain redhat has it precompiled in to the default kernel. Good luck!