The apartment is great: clean and big enough (we were three people). The main entrance of the building is shared between numbers 32 and 33, and the lockbox is located in the 33 door (we arrived at 3am because of a delay in our flight but find the key was very easy, there are two lockboxes, but you need to open the first one).
To reach the city center, you can take any bus in a nearby stop, but if you like to walk, it takes around 35 minutes from the apartment to the city center.
I'll repeat this apartment in my next visit to Dublin :)