switching cam with button?

using UnityEngine;
using System.Collections;
using System;

public class Main_Menu : MonoBehaviour
{

// Use this for initialization
void Start() { }

public bool isStart;
public bool isexit;
public bool isinstructions;

void OnMouseUp()
{
    if (isStart)
    {
        Application.LoadLevel(1);
    }

    if (isexit)
    {
        Application.Quit();
    }

    if (isinstructions)
    {
   
        }

    }

}

}

I have this script set up and but can’t figure out how to have it change cameras after checking “ifInstructions” help please?

add references to the top to your two cameras, use SetActive to toggle within your if(xxx) blocks