1. Is the file in the right place?
T H I S post is a good start to see where all files should be copied to.
2. Did you enable 3D view in your settings?
3. That is all you need.
Now the main issue. Buildings are only visible on limited places on earth, esp. in more important cities (Paris, London, Berlin, and many other, even smaller cities). As a pure example: I guess you will see buildings on your screen in Munich, Germany, but none what so ever in Monschau or Braunlage, also German cities. Honestly, I am not 100% sure about this, because I didn't test if any buildings are visible in those cities. But I do know that the latter two are unimportant cities. (thanks to google maps
).
Anyway, the 3D building feature is rather eye candy. Nice to see but really useful? I don't know, I find my way without seeing any building at all on my screen most of the time.