The easiest way to reach 'Eua is by air. Lulutai Airlines (formerly Real Tonga) operates short flights from Tongatapu's Fua'amotu International Airport, taking about 30 minutes. Flights run most days but the schedule is irregular — book in advance and confirm the departure time before travelling to the airport.
The ferry alternative is a 2–3 hour voyage on the MV 'Otuanga'ofa, which runs several times a week between Nuku'alofa and 'Eua's main port at 'Ohonua. The ferry is basic but functional and gives you a view of the island's dramatic east coast cliffs as you approach. Check the current schedule locally before relying on it, as it changes seasonally.
'Eua is small enough to explore by bicycle or on foot, though the hilly terrain makes cycling demanding. Guesthouses can organise vehicle hire or guided transport to the national park trailheads.