I added an empty drive into one of the spare bays, and then booted from the Proxmox installer.
After first boot and logon with the default root user to the web interface:
The first VM I want to create is for CentOS, and I have the iso ready to go on an attached usb drive, which I copied to the isos dir on Proxmox (/var/lib/vz/template/iso – defined storage locations for images are covered in answers to this post). The image now shows up on the local storage:
Creating a new VM based on this image:
Starting up the image and starting the CentOS install using the web-based vnc access:
… after completing the install, success!