If you need to get access to the main university network from outside the University, even if you still live in Oxford, you need to use the Cisco VPN (Virtual Private Network) client software.
You can find full details on signing up for and using this free software at http://help.it.ox.ac.uk/network/vpn/index. SSO Credentials are required to login to this site.
New College VPN
New College has its own VPN service for staff - details and remote working help in general can be found on the SharePoint HUB.