Set clone as target

How would i go about this you can do it on play game but then it reverts of course im just wondering how would you go about doing this as i need to have it done for my character.

The PlayerHealth is expose to use a clone prefab.

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class UIManager : MonoBehaviour
 {
 
     public PlayerHealth playerHealth;
     public Text HealthText;
 
     private static bool UIExists;
 
     // Use this for initialization
     void Start()
     {
         if (!UIExists)
         {
             UIExists = true;
             DontDestroyOnLoad(transform.gameObject);
         }
         else
         {
             Destroy(gameObject);
         }
     }
 
     // Update is called once per frame
     void Update()
     {
         HealthText.text = "" + playerHealth.currentHealth;
     }
 
 }