1 - Instantiate "ScreenFadeCanvas" prefab
2 - Get WF_ScreenFade from that object
3 - Use the function WF_ScreenFade.ExecuteOnScreenBlack(UnityAction call) to execute something when screen is black.
"call" is the name of the function you want to run.

4 - To adjust the fade speed change FadeIn and FadeOut animations lenght.
5 - Enjoy