This shows how to set up a simple battle scene and how to add code for enemies to fire at. Hope it helps.
Part 1 is here: https://www.youtube.com/watch?v=eg2neHvbfpQ
Part 2 is here: https://www.youtube.com/watch?v=XoYVb8Q42Ec
This is the model I used for the battleship: http://www.turbosquid.com/3d-models/3d-war-navy/409015
Important: Please always note the license agreements associated with any free resources.