You do not need to download Among us Map separately if you are playing online with your friends on Steam, xBox, Playstore, AppStore or BlueStacks. You just have to update the game. But still the Airship map is not yet release and said to be soon released for the public. As soon as the update will release we will upload the download link for the users to download if they are playing offline it might help for them.
If you want to learn more about Among us Airship update CLICK HERE.