For CC, see the FAQ
How can I send to CC book formats with a type (extension) calibre doesn't recognise?. If there is an app on the device that advertises that it handles an extension then CC should find it.
As for the calibre side of things: you can put one file of any given extension into the book record in calibre by dragging the file onto the cover image in book details. There are other ways to do it as well.