Unity 4.6 - How to Move a UI inside of the canvas

hello everyone, i have a question. i'm trying to move a UI element to the center of the screen. I'm using this: newPosition = Camera.main.ScreenToWorldPoint(new Vector2((float)Screen.width/2f (float)Screen.height/2f));

and them this:

iTween.MoveTo(gameObject, iTween.Hash("islocal",true,"x",newPosition.x,"y",newPosition.y, "easeType", "easeInOutCirc", "loopType", "none", "delay", 0.1f));

It worked before, but it seems that in unity 4.6 inside of a canvas doesn't work. Any ideas of how can i move a object to me center of the screen?