You have to use the teleporters to get into the harbor, once you are in there you will see a ramp leading up to the airship, on this ramp is a champion seated in a chair, go talk with him and he will offer you a ride to Aleroth.
As a note I am not sure if you have to repair all the zepplins first or not as I did that anyways before I asked to leave for Aleroth.
