[Alneyan]

There is a file called command_line_switches.txt in your doc repertory. In order to make a shortcut for a game, create a shortcut of your Dominions exe, go to Properties => Shortcut, and select the Target field.

You should add the commands --ipadr [IP] --port [XXXX] after dom2.exe, with the IP of the server and the port of the game. For example, it could give the following for a Mosehansen game (Yarnspinners in my example):
C:\dominions2\dom2.exe --ipadr mosehansen.dk --port 2292

Hope it helps!