How do I hook up to a HP UNIX system using a XP Windows PC and run applications using VPN?

We have an HP UNIX system (1986 - 1993) that is running software on it. I am at a remote site and connect to the network using VPN. After connecting to the network using VPN, I can telnet to the HP UNIX station, but cannot run any applications. I need to run a UNIX system software package, as though I am sitting behind the XP Windows system - Is this possible? What software would be required, and how would I go about hooking it up to make it work?