How do i use unity ads?

Unity Engine
1

I am making a mobile game and am trying to play an advertisement when i press a button. How do i make the advertisement play? I tried something but it doesn’t work.

public void PlayAd()
    {
        if (Advertisement.IsReady())
        {
            Advertisement.Show();
        }
    }
2

https://unityads.unity3d.com/help/unity/integration-guide-unity#rewarded-video-ads