What is wrong with my code?

I was following the survival shooter tutorial on unity’s website for their health and damage scripts so I can learn how to do it. So I followed it I understood it until when I completed the scripts I got an error:
(42,34) CS0120 An object reference is required to access non-static member DamageHandler.currentHealth
(43,39) CS0120 An object reference is required to access non-static member DamageHandler.Damaged(int)
The thing I can’t figure out is why is it saying I have not referenced it I did that in void awake.

Here is my code if you want to look:

using UnityEngine;
using UnityEngine.UI;
using System.Collections;

public class DamageHandler : MonoBehaviour {

	public int startingHealth = 100;
	public int currentHealth;

	public float flashSpeed = 5f;
	public Color flashColour = new Color(1f, 0f, 0f, 0.1f);

	public Slider healthSlider;
	public Image damageImage;

	bool isDamaged;
	bool isDead;

	void Awake(){
		currentHealth = startingHealth;
	}

	void Update(){
		if (isDamaged) {
			damageImage.color = flashColour;
		} else {
			damageImage.color = Color.Lerp (damageImage.color, Color.clear, flashSpeed * Time.deltaTime);
		}
		isDamaged = false;
	}

	public void Damaged (int amount) {
		isDamaged = true;

		currentHealth -= amount;

		healthSlider.value = currentHealth;

		if(currentHealth <= 0 && !isDead) {
			Death ();
		}
	}

	void Death() {
		isDead = true;
		Destroy (gameObject);
	}
}

using UnityEngine;
using System.Collections;

public class EnemyShooting : MonoBehaviour {

	public float attackDelay = 0.5f;
	public int attackDamage = 10;

	GameObject player;
	DamageHandler damageHandler;
	bool playerInRange;
	float timer;

	void Awake () {
		player = GameObject.FindGameObjectWithTag ("Player");
		damageHandler = player.GetComponent<DamageHandler> ();
	}

	void OnTriggerEnter2D (Collider2D other) {
		if (other.gameObject == player) {
			playerInRange = true;
		}
	}

	void OnTriggerExit2D (Collider2D other) {
		if(other.gameObject == player) {
			playerInRange = false;
		}
	}

	void Update () {
		timer += Time.deltaTime;

		if (timer >= attackDelay && playerInRange) {
			Attack ();
		}
	}

	void Attack () {
		timer = 0f;

		if(DamageHandler.currentHealth > 0) {
			DamageHandler.Damaged (attackDamage);
		}
	}
}

The offending code is here:

 if(DamageHandler.currentHealth > 0) {
         DamageHandler.Damaged (attackDamage);
 }

Those DamageHandler references (with a capital “D”) are referring to the DamageHandler class. You want to refer to the DamageHandler instance you cached in the Awake() method. That’s “damageHandler”, with a lower-case “d”.