Have a UI Button do what my Input.GetButtonDown("Use") does?

Hey, I have been working on this for days and can't find anything on this topic. I am switching my game from keyboard controls to Mobile UI Button controls. Everything works perfectly, I have a virtual joystick that works on touch, my jump button works and my attack button works. But I can't get my "use" button to work.

My use input has the keyboard input "f" assigned. So when I press "f" next to a switch it drops a box, or if I press "f" on a level door, I enter that level door. That is because I am using Input.GetButtonDown("Use"); in several IF statements throughout my various scripts.

Now I am trying to replace that pressing "f" or Use buttondown with a UI Button. This seems to be a really easy thing, but it is NOT. I know I can attach a trigger event to my button and do the "Pointer Down (Base Event Data)", as that is what I have done with my jump and attack functions. But it doesn't work with my Use input.

Basically I want this UI Button to have the same effect as pressing the letter "f" on the keyboard. Here is a code example of how I use the letter "f" when I am next to a switch.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI; 
 using UnityEngine.EventSystems; 
 
 public class FallingObject : MonoBehaviour {
 
     public GameObject fallingObject;  
 
     private LevelManager theLevelManager; 
 
     public bool waitingForRespawn; 
 
     public SpriteRenderer leverStart; 
     public Sprite  leverMiddle; 
     public Sprite leverRight; 
 
     public AudioSource leverActivation; 
 
 
     //new try for trigger and button
     private bool triggerEntered; 
 
 
 
      
 
     // Use this for initialization
     void Start () {
 
         theLevelManager = FindObjectOfType<LevelManager> ();
 
 
 
     }
     
     // Update is called once per frame
     void Update () {
 
         if (theLevelManager.respawnCoActive) {
             fallingObject.GetComponent<Rigidbody2D> ().isKinematic = true;
             waitingForRespawn = true; 
 
         }
 
         if (waitingForRespawn && !theLevelManager.respawnCoActive) {
             waitingForRespawn = false; 
             leverStart.sprite = leverMiddle; 
         } 
 
 
         if (Input.GetButtonDown("Use") && triggerEntered == true) {
             
                 fallingObject.GetComponent<Rigidbody2D> ().isKinematic = false;
                 leverStart.sprite = leverRight;
                 leverActivation.Play ();
             
             }
         
             
         
     }
 
     public void useButtonClick(){
         Debug.Log ("the button has been clicked"); 
 
     }
 
 
     //this decides if the player is in the zone of the lever
     void OnTriggerStay2D(Collider2D other) {
 
         if(other.tag == "Player"){
             triggerEntered = true; 
         }
     }
 
     void OnTriggerExit2D(Collider2D other){
 
         if (other.tag == "Player") {
             triggerEntered = false;
         }
     }
     }