Burning a disc is a two-part process. First you must make a disc image using mkisofs. Then you use cdrecord to burn the image onto your recordable CDROM disc. Use apt-get to install both packages. You must install these packages before you set up SCSI emulation, otherwise you will not be able to read the packages from your CDROM drive(s). This is because your CDROM drive(s) will not be recognised until they are re-configured for the emulated SCSI bus.
athlon:/home/chris# apt-get install cdrecord mkisofs
During the installation of cdrecord you are asked whether you want cdrecord to be installed SUID root. This allows users in group "cdrom" to burn CDs. This makes sense on a personal desktop PC. You can change this configuration later using dpkg-reconfigure cdrecord.
Do you want /usr/bin/cdrecord to be installed SUID root? yes
If you do this, don't forget to make yourself a member of group "cdrom". To add user "chris" you would enter:
athlon:/home/chris# adduser chris cdrom
(This may not take effect until after a reboot. Any user can check which groups they belong to using the command groups.)