If you mean host more than four or eight players (depending on what mode you want to do), you'll have to do a lot of adjusting server side to enable that. You'll need to make sure you're running SourceMod and MetaMod on your server, and download the necessary extensions to make it work over at sourcemod.net. I can't really provide too much assistance, as I've never been able to get it to work.
The other thing is that I'm not sure if you need to run a strict dedicated server, or if you can just add the necessary files to your gameplay files, and host locally. Have you looked into setting up your own dedicated server yet?