From the airport a taxi is the easiest solution (1,5 km.)

When arriving at the harbour: You can take the bus at the end of the harbour (4th bus stop is Megali Ammos). The bus leaves every 15 minutes.  The distance from the bus stop Megali Ammos to IRINIS HOUSE: about 100 meters/330 feet).

You can take a taxi from the harbour.

Coming in with your own private boat, you can enter the bay of Megali Ammos, and leave the boat there.