An operating system will be installed by default with your virtual machine.
To re-install an operating system, navigate to your service page and mount an ISO of your choice. Then, log onto Proxmox with credentials provided to you and double click on your service to initiate a VNC session. Reboot the server and install with your configuration through the VNC connection.
Our Canadian services are hosted with OVH.
For network configuration information, please view their support articles.