Hi,
From Rome Airport Fiumecino there is a train (Leonaardo Express) which takes you to the Central Termini train station.
When you walk out of the airport to catch this train, there are lots of booths selling tickets. I think it is about 10E. The trains go every 20 mins or so and the journey lasts 35 mins.
Then when you arrive in the Certral Termini station, you have to walk to a separate part of the train station (about 10 mins down a long platform) to get to the train for naples. There are TV monitors letting you know which platform to go to.
There are many different trains, the best and quickest to get is the EuroStar. The journey takes 2 hrs, and is very comfortable.
I bought my ticktes for the EuroStar before I left (saved having to queue to buy them in Central Termini). The website is
www.trenitalia.it.
To make the connections, give yourself PLENTY of time. I had given myself two hours between the flight arriving and my Naples train. Then my flight was delayed by an hour, and I had to wait at the baggage carousel for 45 mins. I missed my train, and only by running like the wind (panicking trying to find the platform) I just made the next train.
I would say give youself loads of time (at least three hours) to catch your train connections, and find platforms without stressing out.
However, even though I had missed my train, and had to get the next one, there was no extra charge. So if you are delayed and miss your train, they run fairly frequently, so you can just wait around and get the next one.
Enjoy your holiday!
Ragazza.