You buy them as all the other goods on the marketplace. But they need quite a good mix of resources (think min. animal-resources and plant-stuff-like-some-you-know need to have a positive balance) and a tec level of about 3 I think. Otherwise you can buy some of other players, expecially the large ships need a quite high tec level.
After having bougt some, the one way they are in your storage as all the other goods. To use them, you need a Habour. There you can bring them to water an use them as units.
greetings
Florian aka Satanas
I hope there are not that many faults in this one
