navmesh error

Hi ! Im new in unity3d and i need some help...How i can solve this?

if this is

Spoiler: NAVMESHAgent

using UnityEngine;
using System.Collections;

namespace CompleteProject
{
public class EnemyMovement : MonoBehaviour
{
Transform player; // Reference to the player's position.
PlayerHealth playerHealth; // Reference to the player's health.
EnemyHealth enemyHealth; // Reference to this enemy's health.
NavMeshAgent nav; // Reference to the nav mesh agent.


void Awake ()
{
// Set up the references.
player = GameObject.FindGameObjectWithTag ("Player").transform;
playerHealth = player.GetComponent <PlayerHealth> ();
enemyHealth = GetComponent <EnemyHealth> ();
nav = GetComponent <NavMeshAgent> ();
}


void Update ()
{
// If the enemy and the player have health left...
if(enemyHealth.currentHealth > 0 && playerHealth.currentHealth > 0)
{
// ... set the destination of the nav mesh agent to the player.
nav.SetDestination (player.position);
}
// Otherwise...
else
{
// ... disable the nav mesh agent.
nav.enabled = false;
}
}
}
}

 

Follow this tutorial. --> https://unity3d.com/learn/tutorials/modules/beginner/navigation/navigation-overview

It sounds like you didn't "Bake" a navmesh yet. You have to do that in order to tell the NavAgent where is is allowed to go. That tutorial is great. Helped me understand it easily.