Assuming I was asked for install cd1, here is what I would do. Open up an x terminal and give these commands:
fancy@uilleann $ su -
root@uilleann # mount /pub/shrike-i386-disc1.iso /mnt/cdrom -o loop=/dev/loop0
root@uilleann # umount /mnt/cdrom
Of course, the umount command would be used when the package manager is finished with that CD.