If you CD-ROM isn't the first device in the boot order you will need to go into the BIOS and change that. After that with the CD in the drive the computer should boot from the CD when you restart it. The installation disc will prompt you to partition and format the hdd before installing the OS.
If this doesn't cover what you are trying to do please let us know more specifically what you are trying to do.
If you need a tutorial for installing the OS this
one is a good one. The only thing that I don't agree with is the suggestion that you upgrade your BIOS, you should need to do this unless there is a problem with new hardware that it isn't supporting.