Tabarka has a small international airport (TBJ) with seasonal charter flights from France, Italy and Germany. Outside the summer season these are minimal and flying to Tunis-Carthage (about 170km east) and taking a bus or rental car is more practical.
Buses run from Tunis to Tabarka but the journey takes around four hours. From Bizerte the connection is quicker. If you're coming from Algeria, the Ain Draham crossing is nearby, though border formalities can take time. Driving your own car gives the most flexibility — the road through the Kroumirie mountains is scenic and the drive from Tunis takes around three hours.