There are two possibilities:
1) Drive along the Autostrada del Sole via Milan-Bologna-Florence-Rome-Naples-Villa San Giovanni (Reggio Calabria); then take the ferryboat
from Villa San Giovanni to Messina and drive to Erice (350 km from Messina).
2) Take the ferry-boat either from Genoa or Naples to Palermo, and then drive on to Erice (100 km from Palermo). The places on the ferry-boat must be booked in advance.