Hello KR4BR and welcome to the forum!
To play online, you have to patch the game to at least version 1.3
But preferably update it to the latest version, which is 1.42
To download patches, go here (http://www.shipsim.com/downloads/patches.php)
Then simply pick the one that is appropriate for you. You can see which version you are running now, by starting up the game and then you can see your version in the lower left-hand corner of the main menu.
Simply run the patch once you have downloaded it and it will update the game. Then you can pick Multiplayer from the main menu.
Make sure you have your own custom user profile in the game (not the default one) and that you are also in online mode. MP should then start up and show you the server list. Pick one you like and have fun!
Regards,
Fred