In Proxmox shell:
root@pve:~# apt-get update
root@pve:~# apt-get upgrade
root@pve:~# apt dist-upgrade
In Proxmox shell:
root@pve:~# apt-get update
root@pve:~# apt-get upgrade
root@pve:~# apt dist-upgrade
This is the quickest and easiest SSL install for Proxmox I could find. Great little tutorial.