Yep, first of all you need an *.obj file for every part of the ship, in order to import them.
You'll need separated parts for main hull and superstructures, rudder, propellers, masts, funnels, lifeboats, etc, plus guns if you'll not use standard library files.
Open another ship with 3Ditor in order to see the parts you'll need
Let me know when ready for next step!
Best regards,
Vd