Changing scene by clicking on a game object

Hello everyone, firstly I apologize for my basic question, I’m a begginer with programming and can’t get to make this simple action! I have a scene in which I placed four objects, and I want to change to a different scene every time the user presses a game object. I got to do it without a problem by pressing different keys, but when I want to do it by clicking on the objects I get really lost. I tried creating an int that changes value when the user presses the object, but I’m having problems accesing that int from another script. Maybe there is a simple way and I’m not realising it…
This is the code I used for changing scenes with the keyboard:

using UnityEngine;
using System.Collections;

public class SceneManager : MonoBehaviour
{

    static SceneManager Instance;

    void Start()
    {
        if (Instance != null)
        {
            GameObject.Destroy(gameObject);
        }
        else
        {
            GameObject.DontDestroyOnLoad(gameObject);
            Instance = this;
        }

    }

    void Update()
    {
        if (Input.GetKeyUp(KeyCode.UpArrow))
        {
            Application.LoadLevel("2");
        }
        if (Input.GetKeyUp(KeyCode.DownArrow))
        {
            Application.LoadLevel("Demo");
        }
    }
}

Thank you in advance!

I am trying to do the same thing!!
Did you find out how to do this??