Interstitial After GameOver

Hello i have inserted interstitial and banner ads into game ads are showing when you click button, i need to load and start ad after scene starts here is my code please help how can i edit it

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent(typeof(AdMobPlugin))]
 public class Menu : MonoBehaviour {
 
     private const string AD_UNIT_ID = "";
     private const string INTERSTITIAL_ID = "";
 
     private static Vector2 BUTTON_SIZE = new Vector2(100, 50);
 
     private Rect buttonPositionShowAds;
     private Rect buttonPositionHideAds;
     private Rect buttonPositionShowInterstitial;
 
     private AdMobPlugin admob;
 
     void Start() {
         admob = GetComponent<AdMobPlugin>();
         admob.CreateBanner(adUnitId: AD_UNIT_ID,
                            adSize: AdMobPlugin.AdSize.SMART_BANNER,
                            isTopPosition: true,
                            interstitialId: INTERSTITIAL_ID,
                            isTestDevice: false);
         admob.RequestAd();
 
         buttonPositionShowAds = new Rect(
             (Screen.width - BUTTON_SIZE.x) / 2,
             (Screen.height - BUTTON_SIZE.y) / 2,
             BUTTON_SIZE.x, BUTTON_SIZE.y);
 
         buttonPositionHideAds = new Rect(
             buttonPositionShowAds.x, buttonPositionShowAds.y + BUTTON_SIZE.y * 3 / 2,
             buttonPositionShowAds.width, buttonPositionShowAds.height);
 
         buttonPositionShowInterstitial = new Rect(
             buttonPositionHideAds.x, buttonPositionHideAds.y + BUTTON_SIZE.y * 3 / 2,
             buttonPositionHideAds.width, buttonPositionHideAds.height);
     }
 
     void OnEnable() {
         AdMobPlugin.AdClosed += () => { Debug.Log ("AdClosed"); };
         AdMobPlugin.AdFailedToLoad += () => { Debug.Log ("AdFailedToLoad"); };
         AdMobPlugin.AdLeftApplication += () => { Debug.Log ("AdLeftApplication"); };
         AdMobPlugin.AdOpened += () => { Debug.Log ("AdOpened"); };
 
         AdMobPlugin.InterstitialClosed += () => { Debug.Log ("InterstitialClosed"); };
         AdMobPlugin.InterstitialFailedToLoad += () => { Debug.Log ("InterstitialFailedToLoad"); };
         AdMobPlugin.InterstitialLeftApplication += () => { Debug.Log ("InterstitialLeftApplication"); };
         AdMobPlugin.InterstitialOpened += () => { Debug.Log ("InterstitialOpened"); };
 
         AdMobPlugin.AdLoaded += HandleAdLoaded;
         AdMobPlugin.InterstitialLoaded += HandleInterstitialLoaded;
     }
 
     void OnDisable() {
         AdMobPlugin.AdLoaded -= HandleAdLoaded;
         AdMobPlugin.InterstitialLoaded -= HandleInterstitialLoaded;
     }
 
     void HandleAdLoaded() {
 #if !UNITY_EDITOR
         admob.ShowBanner();
 #endif
     }
 
     void HandleInterstitialLoaded() {
 #if !UNITY_EDITOR
         admob.ShowInterstitial();
 #endif
     }
 
     void OnGUI() {
         if (GUI.Button(buttonPositionShowAds, "Show Ads")) {
 #if !UNITY_EDITOR
             admob.ShowBanner();
 #endif
         }
 
         if (GUI.Button(buttonPositionHideAds, "Hide Ads")) {
 #if !UNITY_EDITOR
             admob.HideBanner();
 #endif
         }
 
         if (GUI.Button(buttonPositionShowInterstitial, "Show Interstitial")) {
 #if !UNITY_EDITOR
             admob.RequestInterstitial();
 #endif
         }
     }
 }