Hello Capn Jon,
It depends on what version you are running atm.
If you allready have V1.1, then you can grab the V1.1 to V1.3 patch. (227MB)
But if you are running V1.0, you grab the V1.0 to V1.3 patch. (568MB)
Link to the pacthes: http://www.shipsim.com/downloads/patches.php
If you are not sure what version you are running, you can see this in the lower left hand side of the screen on the main menu in the game.
Regards,
Fred