I know this isn't that the replace to ask, but not sure where to go. Where should I ask about setting up a VPN on the supplied Techicolor MediaAccess TG589vac v2 router/modem? It doesn't seem possible to me, but the user interface isn't great and I can't see anything in the user guide.
I don't think you can run a VPN client (or server) on that router. VPN traffic from a VPN client (or server) on a PC or other device would likely pass through it.
If you wish to connect to public VPN servers, I would expect them to tell you how to configure your client.
Why do you want a VPN. What are you trying to connect to what? I have managed to install VPN servers on two different NAS devices at home using Openvpn protocol. I can use a VPN client on my laptop to connect to these servers from other locations.