Flight
Rome is about 4.5 hours away from Positano by car, and is also reachable with public transportation.
Flight
There is a ferry that shuttles from Naples to Positano, approximately a one-hour 45 minute ride. The ferry was recommended by various travel blogs for a superb view of the Almafi Coast. You can also use private car rentals, taxi services, or other public transportation.
Travel Note
Positano is a relatively small town, there are a decent number of hotels but they can fill up quickly and can be pricey. There are quite a few towns surrounding Positano as well that also have accommodations. Check discount sites like booking.com for better deals too!