iTween in unity 3d?

Hi All,

I am new to unity. now i am working on the gui text animations. for that i searched in the Google and i find itween.

i just crated a new unity project. In that i wrote script like this

     using UnityEngine;
     using System.Collections;

      public class Move : MonoBehaviour {

 // Use this for initialization
 void Start() {
     iTween.MoveTo(this.gameObject,iTween.Hash("x",transform.position.x+3,"time",3));
     } 
 
 // Update is called once per frame
 void Update () {
 
 }
     }

after saving my script i got one error like:

The name `iTween' does not exist in the current context

In a empty project i didn't import any plugins and any thing.

Can i get the correct procedure for creating and using that itweens.

thanks in advance

Navadeep