There are daily buses from Athens to Nafpaktos and the trip takes about 3 hours. Buses from Athens depart from Kifissos KTEL Bus Station (Bus 051 Omonoia-Kifissos and Bus X93 Athens Airport-Kifissos).
There are also buses to Nafpaktos from many other towns of Greece, including Patra and Thessaloniki. These bus schedules may not be daily but two or three times a week.
To go from Athens to Nafpaktos by car, you take the National Highway Athens-Patras. After you cross the cable bridge of Rio-Antirio, you follow the signs to Antirio and Nafpaktos.