You need a BB data plan (or bolt on) to display maps on the device. Maps are downloaded as needed and not stored on the device. Once you get a proper data plan, then BB Maps should be pushed witht he service books. You can also download and install Google Maps.
However, if you are expecting a true GPS-like experience, you won't get it. You need to either subscribe to your carrier's version of TeleMaps at an extra charge or buy a stand alone GPS device. The latter is probably the better option since it is probably cheaper int he long run and doesn't rely on a cell signal to operate.
Check the GPS and Maps section for more information.