Airport:

Fiumicino - Roma
Perugia S. Egidio

Motorway:

A1 Roma-Firenze(exit Orte) go on to Orte-Terni road (exit Terni ovest)

Train:

Roma-Ancona line (get of at Terni station).
Roma-Firenze line (get of at Orte station) and catch the train to Terni.