Avellino is a city in the Campania region of Italy.
By bus from Capodichino international airport (Naples). Ticket is only 3.4 euro. You can go also by taxi for "special price only for you" - 100 euro. There are some car rentals directly on the airport.
City is small enough to get around by foot. There are some buses but I couldn't find any plan online and plans on stops are burned by sun (totally white - you cannot see anything). You must buy a ticket in a stand and it's valid for a certain timespan. Google maps route finder gives good approximates for walking distances and walking times around a city