How can I set up a sub MS (using sub-domains) network on my root domain?

I have my MS network installed on my root domain (using sub-directories), which is http://www.torsnet.com. I want to be able to use my http://www.torblogs.com domain as a secondary MS install, using sub-domains. I know that it's possible, I just don't really have a clue how to go about it.