Need help in coverting Republique based asset game to use Networking

I am new to Unity and I am trying to convert the republique game to use networking. I am following http://docs.unity3d.com/Manual/UNetConverting.html to convert. At step where we create a prefab I see that the scene goes blank.

Anyone had a similar experience and tips or suggestions to follow to convert the game to use Networking.

I get the following error.
Failed to create agent because it is not close enough to the NavMesh...

Need help in coverting Republique based asset game to use Networking