On the motorway towards Rome, take the Exit "Roma Nord", you will be on the Beltway (follow direction Napoli-Tiburtina or Roma-Aquila).Take exit number 13 (Tiburtina, direction centro), follow all the way trough. You will find yourself on "Piazzale del Verano". From there, take" Via C.De Lollis". When you see the archs coming up, pass them and take a right onto "Viale Castro Pretorio". You are now very next to the Subway line B "Castro Pretorio" and when you see the sign "M" turn to the left and you've get Via S.Martino della Battaglia.
Exit the motorway in the Roma beltway (direction Firenze-Tiburtina), take exit number 13 (Tiburtina, direction centro), follow all the way through. You will find yourself on "Piazzale del Verano". From there, take Via C.De Lollis. When you see the archs coming up, pass them and take a right onto Viale Castro Pretorio. You are now very next to the Subway line B "Castro Pretorio" and when you see the sign "M" turn to the left and you've get Via S.Martino della Battaglia.

Fiumicino airport (Leonardo da Vinci)