Remote connections
It is possible to play the game over a network connection with another computer. One of the computers will act as game server. This one can determine who should play which color. You can configure the network options in the game menu, network dialog. There you also find a chat dialog box which allows you to speak with your friend.
When a network connection is build you are asked to enter a remote host and a port. The port can usually just be left untouched, but if you know what you are doing replace it by another number, which has to be the same in both player games of course. The hostname should be the name of the remote host to which you are connecting. Only the client in the connection has to supply a hostname. It is often wise that the player behind a firewall chooses to be client as the firewall might not allow incoming connections.