Ending the Game

I'm wondering how I should make my game end after my player comes in contact with my check point which is a flag. The code for my flag: using UnityEngine; using System.Collections; public class CheckPoint : MonoBehaviour {

     public Sprite redFlag;
     public Sprite greenFlag;
     private SpriteRenderer checkpointSpriteRenderer;
     public bool checkpointReached;
 
     // Use this for initialization
     void Start () {
         checkpointSpriteRenderer = GetComponent<SpriteRenderer> ();
     }
 
     // Update is called once per frame
     void Update () {
 
     }
 
     void OnTriggerEnter2D(Collider2D other){
         if (other.tag == "Monkey") {
             checkpointSpriteRenderer.sprite = greenFlag;
             checkpointReached = true;
         }
     }
 }

And the code for my player: using UnityEngine; using System.Collections; public class Monkey : MonoBehaviour {

             public Rigidbody2D rigidBody;
             public float mooooove;
             public float moveSpeed;
             public float jumpSpeed = 8f;
 
 
             void Start () {
                     rigidBody = GetComponent<Rigidbody2D> ();
                 }
             void Update () {
                     mooooove = Input.GetAxisRaw ("Horizontal");
                     if (mooooove != 0) {
                             rigidBody.velocity = new Vector2 (mooooove*moveSpeed,rigidBody.velocity.y);
                             transform.localScale = new Vector3 (mooooove,1,1);
                         }
                     if (mooooove == 0) {
                             rigidBody.velocity = new Vector2 (0,rigidBody.velocity.y);
                         }
                     if(Input.GetButtonDown ("Jump")){
                     rigidBody.velocity = new Vector2(rigidBody.velocity.x,jumpSpeed);    
         }
     }
 }