Buy the download version, open the game, and in the bottom left corner, it will say version X.X. So basically,the version number. If it says 1.1, then you need to download 1.3 off www.shipsim.com for multiplayer.
On shipsim.com, there is a page called My Orders. You have to register on the website to buy SS. Type in your password and email adress, and the links for the downloads will be there. That way, if your bro uninstalls SS, you can re download it
If you want anything else, just say