NetworkTable isn't an object, per se; the NetworkTable protocol (FRC-specific) is used in communication between the robot and anything else you can have on your network.
In RoboRealm, you can go here:
http://www.roborealm.com/FRC2013/index.php and scroll down to the last tutorial.
The robot acts as the main server, distributing the tables [maps - key/value pairs] to all the clients it connects to. You can view all the data in the network tables in the JAR file: C:/WindRiver/WPILib/TableViewerr355.jar
Keep in mind that ANY entry that has a name that begins with /SmartDashboard/... will be shown on the smart dashboard, regardless of the source (Assuming you're connected to the robot).
In TableViewer, when it asks you for the ip address, put in the ip address of your robot. I believe port number should default at 1735.