HostBill installation is fully automated and takes just seconds, more info at Installation
Proxmox v2 module allows you to use NoVNC console. To enable it, copy file _upload_proxmox/vncconsole.html from module directory and upload to your Proxmox servers into directory:
/usr/share/novnc-pve/
Now your customers will be able to access noVNC console.
Important: Make sure to install valid SSL certificate for your Proxmox server, otherwise your customers will not be able to see noVNC console.