You won't be able to cd directly into the device. What you need to do is mount the device to a directory. If you take a look in your /etc/fstab file, you should see a line that looks like
/dev/hdc /mnt/cdrom iso9660 defaults,ro 0 0
If that's the case, then all you have to do as root is
and you should now be looking at the contents of your CD.
If the line is missing let us know and we'll help you out from there.