How am I able to PUT SOUND

using UnityEngine;
using System.Collections;

public class DiEps : MonoBehaviour {

void Update () {
	
	
	System.DateTime threeHrsFromStart = System.DateTime.Now.AddMinutes(3);
	
	
	if (System.DateTime.Now - threeHrsFromStart > System.TimeSpan.FromMinutes(3)){

		//I need to place here a sound. How am I able to call it in here.

It will be somehow, like an alarm clock. after the time ends it will ring.

	}
}

}

You attach an audio source component to your object, set the relevant options and then call audio.Play();