I have been working on Help pages to explain how to add new categories... I added the section on the Royal Australian Navy categories so that it now shows the help section. Go there and select the help topic to create new ships and see if that explains it well enough for you to add the ships (they show in red if not created, but anyone can add categories, it is not limited to supervisors).
if you run into problems, let me know so I can update the help instructions to make them easier to follow....