UnityEngine.UI and UnityEngine.EventSystem do not work, what do I do?

hello i am new to unity and im trying to script joystick but i get an error before i even write any functions. I have no clue about anything that is before the public class Script_Name {} because i have never worked with it before.

"'Virtual_Joystick' does not implement interface member 'IPointerClickHandler.OnPointerClick(PointerEventData)'"

using UnityEngine;

using UnityEngine.EventSystems;

using UnityEngine.UI;

using System.Collections;

public class Virtual_Joystick : MonoBehaviour, IDragHandler, IPointerUpHandler {

 // Use this for initialization
 void Start () {
 
 }
 
 // Update is called once per frame
 void Update () {
 
 }

}

please help, thank you very much!