error in xml script

for xml i used script

using UnityEngine;
using System.Collections;
using System.Xml;

public class XMLEditor : MonoBehaviour

void Awake()
    TextAsset textXML = (TextAsset)Resources.Load("myxml.xml", typeof(TextAsset));
    XmlDocument xml = new XmlDocument();


gets error

NullReferenceException: Object reference not set to an instance of an object

XMLEditor.Awake () (at Assets/XMLEditor.cs:13)

how to escape from this error

The file must be in the root of a Resources folder somewhere within the project