This will change scene all time when you click left mouse button. But you need change scene when clicking on Cube. Try this
EDIT: Create new C# script named SceneChange.cs
using UnityEngine;
using System.Collections;
using UnityEngine.SceneManagement;
public class SceneChange : MonoBehaviour {
Ray ray;
RaycastHit hit;
void Update()
{
ray = Camera.main.ScreenPointToRay(Input.mousePosition);
if (Physics.Raycast(ray, out hit) && Input.GetMouseButton(0))
{
if (hit.collider.name == "cubone")
{
SceneManager.LoadScene("scena2stanza");
}
}
}
}