How do you create a Garry's Mod 9.0.4 server?

Sorry if this is the wrong section, or if this is a really stupid question, but I was wondering how to create a Garry’s Mod 9 server? I’ve never set up a server before, but I have some friends I want to play with on Garry’s Mod 9.0.4 so I just want to play with them. Thank you in advance.