Set the location of your airship by right-clicking on a tile and choosing Set Location > Airship (sorry if the terms are wrong - I'm at work and don't have the engine with me).
If the player can walk up to the airship and board it, you don't need to do ANYTHING else. The airship vehicle already has the correct setup for this.
If you want to come from ANOTHER map or have your PC walk to the airship and board it after talking to an NPC, you will either use a Transfer Player command or a Set Move Route command to put the player on the same map as the airship, standing one tile below (above/beside) it, facing the airship, and then use the Get On/Off Vehicle command.