Need help with "MoveTo" and NavMeshAgent

I’m new to coding and just follow with a tutorials on a book.
And here is the problem:

it tells me that i don’t have a NavMesh yet,
but i had

the enemy does not go towards the player at all !
i don’t know what’s wrong

here is the code

please text all of the right codes~
regards.

Why do you need someone to write you a script while Unity provides it ?
http://docs.unity3d.com/Documentation/ScriptReference/NavMeshAgent.SetDestination.html
Check the script ref first.