How to make the AI use the grid

I have a grid which makes a path towards my player but I seem to be stuck as to how to make my enemy move help.

Here’s something I got online:

using UnityEngine;
using System.Collections;

public class Enemy : MonoBehaviour {
        //deathDistance is basically just if the players enters this radius the 
        //enemy will do something to the player, like kill them.
	public float deathDistance = 0.5f;
	public float distanceAway;
	public Transform thisObject;
	public Transform target;
	private UnityEngine.AI.NavMeshAgent navComponent;

	void Start() 
	{
		target = GameObject.FindGameObjectWithTag("Player").transform;
		navComponent = this.gameObject.GetComponent<UnityEngine.AI.NavMeshAgent>();
	}

	void Update() 
	{

		float dist = Vector3.Distance(target.position, transform.position);

		if(target)
		{
			navComponent.SetDestination(target.position);
		}

		else
		{
			if(target = null)
			{
				target = this.gameObject.GetComponent<Transform>();
			}
			else
			{
				target = GameObject.FindGameObjectWithTag("Player").transform;
			}
		}
		if (dist <= deathDistance)
		{
			//KILL PLAYER
		}
	}
}
Make sure you have your player's tag set to "Player" and that you have the Nav Mesh Agent component on the enemy.  After that it's just left to tinkering.