Ad integration
In Unity, it is very easy to integrate ads in your games using Unity Ads. In Unity, go to Windows | Services and a new tab will open on the right:

In the Services tab, log in with your Unity login and password that you obtained while registering on Unity.
Click on the Create button. This will show the different services that are available to you:

Click on the SERVICES tab:

Flip the switch on the top right corner to enable it. If the game is targeted at kids under 13 click the checkbox and click on the Continue button:

Select Android as the target platform, and check the Enable test mode option, so that we can test it before we publish the game. Now, in the gamescript class, at the top of the class add the following:
using UnityEngine.Advertisements;
All we have to do is call the ShowAd function when we want to show an ad. We don't want to show an ad when the player has an achievement as we also don't want to show the ad every time we call the ShowAd function in the else statement...