Please note: there is a "Milos, Greece" outside of Athens that may appear if you search for Milos on Google Maps. This is NOT the island of Milos. Milos is in the Cycladic island chain closer to Crete than Athens.
You will first book a flight from your home airport to Athens International Airport. If you don't care to explore Athens, you can book a hotel near the airport and fly to Milos the next day for convenience. Alternatively, you can book a hotel in the city center and explore Athens for a day or two before heading to Milos.
You will have to book a separate flight from the Athens airport to the island of Milos, Milos has a small airport and only hosts flights to and from Athens. Flights operate multiple times a day via Olympic Aegean Air or Sky Express, we recommend doing a Google flight search (ATH to MLO) to see your options and pricing.
Ferries are one of the most common ways to get around the islands and are an alternative to getting to Milos if you do not want to take a flight. All ferries to the Cyclades start from Piraeus Port in Athens.
From the Athens airport to Piraeus Port, it is 45 minutes by taxi (~€60), 1h by train (€10) or 1.5h by bus (€6). If it interests you, we do recommend spending a full day in Athens to see the Acropolis and explore the city. If you stay in the city center, it will only take 15 minutes by taxi to get to Piraeus Port.
The main ferries that operate from Athens to Milos are SeaJets and Minoan Lines, with SeaJets being the faster (albeit more expensive) ferry. As an example, Seajets offers a direct fast ferry that is 2.5h and Minoan Lines offers a direct "slower" ferry that is 4h.
You can book your ferry tickets with ferryhopper.com
In addition to Athens, you can also take the ferry to Milos from other islands in the Cyclades as they are well connected by the ferry system. Seajets offers connections between these islands and Milos:
Mykonos to Milos: 2h
Paros to Milos: 1.45h
Santorini to Milos: 2h
If you are traveling within Europe prior to the wedding, it may make sense to fly into other islands within the Cyclades that have airports like Mykonos, Santorini, or Paros as many airports have direct flights to Mykonos or Santorini. The advantage of flying directly to these islands is that the distance between the airport and ferry terminal is much shorter than in Athens.