How to pick up an object when touching a button(Mobile)

Basically i'm trying to duplicate this script so that when i tap a button on screen it will pick up the object. ATM the way it works is when an object has the pickupable script you can press e and it picks it up.

using UnityEngine; using System.Collections;

public class PickupObject : MonoBehaviour { GameObject mainCamera; bool carrying; GameObject carriedObject; public float distance; public float smooth; // Use this for initialization void Start () { mainCamera = GameObject.FindWithTag("MainCamera"); }

 // Update is called once per frame
 void Update () {
     if(carrying) {
         carry(carriedObject);
         checkDrop();
         //rotateObject();
     } else {
         pickup();
     }
 }

 void rotateObject() {
     carriedObject.transform.Rotate(5,10,15);
 }

 void carry(GameObject o) {
     o.transform.position = Vector3.Lerp (o.transform.position, mainCamera.transform.position + mainCamera.transform.forward * distance, Time.deltaTime * smooth);
     o.transform.rotation = Quaternion.identity;
 }

 void pickup() {
     if(Input.GetKeyDown (KeyCode.E)) {
         int x = Screen.width / 2;
         int y = Screen.height / 2;

         Ray ray = mainCamera.GetComponent<Camera>().ScreenPointToRay(new Vector3(x,y));
         RaycastHit hit;
         if(Physics.Raycast(ray, out hit)) {
             Pickupable p = hit.collider.GetComponent<Pickupable>();
             if(p != null) {
                 carrying = true;
                 carriedObject = p.gameObject;
                 //p.gameObject.rigidbody.isKinematic = true;
                 p.gameObject.GetComponent<Rigidbody>().useGravity = false;
             }
         }
     }
 }

 void checkDrop() {
     if(Input.GetKeyDown (KeyCode.E)) {
         dropObject();
     }
 }

 void dropObject() {
     carrying = false;
     //carriedObject.gameObject.rigidbody.isKinematic = false;
     carriedObject.gameObject.GetComponent<Rigidbody>().useGravity = true;
     carriedObject = null;
 }

}