object reference not set to an instance of an object JavaScript

First off, i am very new to unity so it may be obvious what the problem is.

I am trying to make my cube box collider switch of when a button it pressed. My Code:

var Item1 : GameObject;

function Start () {

Item1.BoxCollider.enable = false;

Unity keeps throwing the error “object reference not set to an instance of an object”
What am i doing wrong and how do i fix it?

Click the Item1 (you should added above script to this Item1) in hierarchy window.
Check in the Inspector window where is your script is added to the Item1 and add the reference of that object from asset or from scene.alt text