Hi,
Register your ShipSim license key on your forum profile..
Make sure you have the 1.3 patch, if not go onto the main website http://shipsim.com and click patch's on the left and download and install the 1.3 patch...
Once you've done that, open ShipSim and click profile, have you put the correct username on there?
Once you've done that make sure the 'Allow internet access' checked..
Also check if your firewall is blocking questviewer
Once you've done that you should be able to go on multiplayer by going to the main menu on ShipSim and press 'Multiplayer', there you get a list of servers available..