interstitial_adv.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Advertisements;

public class InterstitialAdManager : MonoBehaviour {

    #if UNITY_IOS
    private string gameId = "3685328";
    #elif UNITY_ANDROID
    private string gameId = "3685329";
    #endif

    public string placementId = "video";
    public bool testMode = true;

    void Start() {

        // Initialize the Ads service:
        Advertisement.Initialize(gameId, testMode);

        // Show an ad:
        StartCoroutine(ShowInterstitialAdWhenReady());
    }

    IEnumerator ShowInterstitialAdWhenReady () {
        while (!Advertisement.IsReady (placementId)) {
            yield return new WaitForSeconds (0.5f);
        }
        Advertisement.Show();
    }
}