vpn

I am new at working with VPNs, I am working with Windows XP at my office and home and two other employees at their home. I would like to set up a VPN to be able to connect to my office computer even when someone else is logged in at the same time, and have security. I have DSL and am working with “Go to my PC” but I cannot log in when someone else is logged on. So my questions are; Do I need anything special as far as hardware to start and install a VPN? What are the steps to install a VPN in the office PC (main) and the other PCs? How do I begin (Installation Process and after it is installed) How do I start the VPN connection to the office from another PC? Tell me everything I need to know as if you were instructing a new student (or baby). Thank you very much.