How can i add a new ship to the game ?
For such a simple question it's actually quite a long and complex answer. Distilled down to the basics, you need a mesh of the ship, you need textures for the ship, you need to add the infocard entries into the string file, you need to add it to a few places in the galaxy scenario def file to allow it to appear in the game, you need to add in the entity file for the ship so the game knows what it is and how it works as well as any entities needed for special abilities that you've given to it, you need to add in the effects for any custom abilities created, and finally, you need to add the ship to the player(race) file in the proper section for each faction that you plan on allowing to build it. It's probably best to start off customizing an existing ship until you're familiar with the process.
Visit MyFist0's site http://soase.x90x.net/ for a much more inclusive and thorough explanation of the process as well as guides to help.
Resistance is futile there I think.
I can resist just fine, cancelled my preorder when it was announced and have absolutely no intention of ever dealing with Steam or Valve ever again. I gave my word on that and when I give my word, it may as well be chiseled in stone because I don't ever go back on it. It's called integrity. ;]