Ischia can be reached from Naples via ferry or hydrofoils from three harbours: Molo Beverello/Porta di Massa, Mergellina and Pozzuoli.
The nearest to railway station and airport is Molo Beverello.
Beverello and Porta di Massa are two different boarding piers (depending on the ferry company) at walking distance from each other within the harbour (see map).
For those who want to arrive by car they must necessarily take a ferry. Boarding points are Porta di Massa Pier in Naples and the Port of Pozzuoli. For those who want to use the hydrofoil (only pedestrians) boarding points are the Beverello Pier and the port of Mergellina.
Ferry timatables can be found on the Airport site or here. Prices and reservations can be found on ferry company sites.
Be aware that the Island of Ischia has three landing harbours: Ischia Porto, Forio and Casamicciola. Be sure to take the line to Ischia (Porto).
From Airport:
take the Alibus (here the official page) from the Airport to Piazza Municipio, then walk to the harbour. Tickets can be purchased at the airport (3.00€) or onboard (4.00€).
Alternatively, a cab from the Airport to the Harbour (Molo Beverello - Imbarchi per Ischia) has a fixed cost of 19.00€, in case the taxi driver asks for more, refer to this document.
From Railway station:
You can either take the Alibus from Piazza Garibaldi (200 mt from the station) to Piazza Municipio and then walk to Molo Beverello, or take the Linea 1 Metro line from Piazza Garibaldi to Università (1.00€) then walk to the harbour, (refer to map).
To the Hotels:
Ischia Porto is about 500mt from the Regina Palace Terme Hotel and about 1 Km from the Hermitage & Park Terme Hotel. You can reach your hotel by taxi or bus (see map).