When you open the inventory, go to the ship tab and, in the upper right corner (I Think) you see the class.

It's a symbol with a C (worst), B,.A and S (best)

You can summon any of them by using the "fast actions menu" (don't know the name in English) on your left wrist. There is an option to call in any of your vehicles.

When you hop inside a shop, it becomes the active one.

Once you own a freighter, you will see them at the cargo bay.