How to use delegate and event in Unity

GameSystem.cs

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

public class GameSystem : MonoBehaviour 
{

	public delegate void Route();
	public static event Route OnPlay;
	
	
	void Start () 
	{
		OnPlay += defaultOnPlay;
		
		StartCoroute(delayStart());
	}
	
	//Helper
	IEnumerator delayStart()
	{
		return yield  new WaitForSeconds(3);
		
		OnPlay();
		
		Debug.Log("Game Started....");
	}
	void defaultOnPlay()
	{
		//do something
	}
}