Switching PC control to mobile

How can I make the cube move left n right with mobile buttons or controls
Here is my script:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerMovement : MonoBehaviour {

public Rigidbody rb;

public float ForwardForce = 2000f;
public float SideWaysForce = 100f;
float moveVelocity ;

// Use this for initialization
void Start () 
{
	

}

// Update is called once per frame
void FixedUpdate () 
{

	// Add a ForwardForce
	rb.AddForce (0, 0, ForwardForce * Time.deltaTime);

	// For PC Control

	if(Input.GetKey(KeyCode.RightArrow ))
	{
		rb.AddForce (SideWaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
	}

		

		

	if(Input.GetKey(KeyCode.LeftArrow))
	{
		rb.AddForce (-SideWaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
	}

	if (rb.position.y < -1f) {

		FindObjectOfType<GameManager> ().EndGame();

	}

}

}

Thankyou in advance.

@Blank1290
keycode.LeftArrow and KeyCode.RightArrow does not work
it gives errors for me

ArgumentException: Input Key named: keyCode.LeftArrow is unknown
UnityEngine.Input.GetKey (System.String name) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/InputBindings.gen.cs:446)
spheremovement.FixedUpdate () (at Assets/scripts/spheremovement.cs:25)