[libvirt-users] Debug VM boot from ISO issues

I'm having trouble booting a VM from an ISO, but my problems may not be virtualization issues, just general confusion. I'm running virt-manager on Ubuntu, but I need to boot a VM with an ISO that is based on CentOS. Is that possible? How do I define the VM in virt-manager to boot from an ISO? I initially created the VM with virt-install, but I started over with virt-manager, and now I'm not sure how to specify the ISO to boot from.