how can i make simple combo attack,,

need help guys. I want to make simple combo attack, just like most game fighting. When i press onetime then playing attack1, when i press twotime then playing attack1 and attack2, and so on. Please help me,, this my script :

  using UnityEngine;
  using System.Collections;
  
  public class Punch : MonoBehaviour
  {
      private Animator animator;
  
      // Use this for initialization
      void Start ()
      {
          animator = GetComponent<Animator>();
          animator.SetBool ("Attack1", false);
          animator.SetBool ("Attack2", false);
          animator.SetBool ("Attack3", false);
          animator.SetBool ("Attack4", false);
      }
      
      // Update is called once per frame
      void Update ()
      {
      }
  
      public void Attack1() //i'm gonna put this on ui image
      {
          animator.SetBool ("Attack1", true);
          print("This Attack 1");
      }
  
      public void Attack2() //i'm gonna put this on ui image
      {
          animator.SetBool ("Attack2", true);
          print("This Attack 2");
      }
  
      public void Attack3() //i'm gonna put this on ui image
      {
          animator.SetBool ("Attack3", true);
          print("This Attack 3");
      }
  
      public void Attack4() //i'm gonna put this on ui image
      {
          animator.SetBool ("Attack4", true);
          print("This Attack 4");
      }
  }

and this my animator :