The location is brilliant. A two minute walk from Garibaldi central station where you can get the yellow and blue metro lines. Ticket machines a little confusing if you dont speak good italian so go to a ticket booth and buy in person. The apartment is above a fantastic pasta and pizza restaurant Da Donato (best to book. Not open on Mondays).
The apartment has a lovely balcony and everything you need; air con, washing machine, cooker, fridge, microwave, hot water, towels and cutlery, plates etc.
If you book any excursions then the pick up point is usually the Star Hotel Terminus which is a 3/4 minute walk from the apartment. Make sure you check though! We booked an Almalfi Coast full day tour and Pompeii half day trip through 'Viator' and the pick up point was there. Very convenient!
There is a little supermarket directly opposite the apartment but I would advise going to the one near the station (you have to cross the road) Sapori and Dintorni Conad.
Napoli is a busy, bustling city so the apartment can be a little noisy at times. This is to be expected and shouldn't affect your stay. I would advise getting a taxi from Napoli airport and back. Francesca (Davide's friend who greeted us) booked our return taxi for us which was really helpful. It was €16 which was better than the €25 we had paid to get there. I wouldn't advise that you drive in Naples, the roads are a little crazy at times! Public transport is easy.
I would recommend going to Da Michele for pizza whilst you're there. Just €4.50 per pizza (all food is generally cheap in Naples). Usually very busy so best to take away for quick service if you don't mind not sitting in. It's a 10 minute walk from the apartment. It's featured in the Julia Roberts film 'Eat Pray Love' and one of the most famous Pizzerias in the city.
Overall a great stay, would recommend!