There are two basic ways of doing MP in Dom3. Direct Connect (which plays like a solo game but with more people) or by file transfer. The most popular method of file transfer is by email. Emailing your action file to a server, which runs the hosting, then it emails your turn back to you.
Email games usually go thru LLamaServer.net which makes it very easy. As far as your menu goes, once you get the turn file into the proper savegame directory, you just open it like a local game. Here is a help file on that
http://forum.shrapnelgames.com/showp...16&postcount=2
Direct connect goes thru the Network menu. You have to know and tell your Dom3 the address of the server the game is on, and the port number its running on there. Other than that it plays like a solo game. Here is a help file on that
http://game.dom3minions.com/how-to.html
In both cases, you first need to go to the Game Tools menu and create a pretender suitable for uploading.
If you want to test MP play there are two ways to get into it more smoothly than just "diving in". One is to go ahead and join one of the "always open" games on the Dom3Minions.com server. Such as a vsAI game which you can start with only one player (since it has computer players in it). You will find them slightly better than the AIs you played in solo games. That will give you an idea if there are any problems such as firewall or router getting in the way, without holding up other people who are wanting to get the game started. If you have a problem running one of those, just ask.
http://www.dom3minions.com/HostedGames.htm
The other method is to start reading the MP subforum here and watch for requests to substitute for someone.
Good luck.
Gandalf Parker