The guide is hosted on the ISBoxer.com wiki:

HOWTO: Launch multiple instances of Star Wars: The Old Republic on the same PC

Launching multiple instances of Star Wars: The Old Republic on the same PC is not normally possible. However, ISBoxer makes launching multiple copies of SWTOR possible through virtualization technology built into Inner Space (the gaming platform that ISBoxer configures for multiboxing).
If you have additional questions, feel free to start a thread here or on the ISBoxer.com forums, etc.