If it was setup when you installed your distribution, then mounting a CD from the terminal is pretty easy. My CD-ROM drive is mounted as /dev/cdrom. Your's may be /mnt/cdrom. So, try both and use the one that works. Put your new CD in the drive, and then from the terminal prompt, type mount /dev/cdrom and hit enter. You should now be able to cd to /dev/cdrom and read the contents of the CD. Once you're done, cd out of /dev/cdrom (or you'll get a wacky message when you do this next command). Now, to unmount the CD so you can eject it, type umount /dev/cdrom and hit enter. And, if you're lazy and want to eject the CD from the command prompt, you can run eject /dev/cdrom