The apartment is very close to the central train station, and the communication with the owner and the lady that maintains the apt was immediate and thorough (they even used Google translate to speak to us in our native tongue!).
However, be aware that there is no elevator, and the stairs are of old style- kind of steep and tall. If you are travelling in the summer, be aware that Naples is super humid and hot, so climbing up 4 flights of stairs after a long day is the cherry on top.
Additionally, the neighbourhood might seem a bit sketchy but during the night there's hardly anyone around that would make you uncomfortable (and we were two girls travelling alone). So, nothing to fear! :)