Unity 2D Car Side Scroller question.

So I'm making a 2D Car Side Scroller for Android. I've got the car working with colliders and all. But the script I'm stuck on.

I've got a working car script, but it only takes in inputs from keyboard and I'm looking for a way to move with buttons. I've already set up a Brake and Accelerate button UI now I just need the script. And I've tried so many things, tried all the Input.touches, GetTouch. And I couldn't find any help online so I thought I'd ask here.

Here's how the script works if anyone can help me manage to get it working with the Unity UI for touch input.

 using UnityEngine; 
 using System.Collections; 
 
 
 public class WheelJointCarMovement : MonoBehaviour {
     WheelJoint2D[] wheelJoints;
     public Transform centerOfMass;
     JointMotor2D motorBack;
     public float dir = 0f;
     float torqueDir = 0f;
     float maxFwdSpeed = -5000;
     float maxBwdSpeed = 2000f;
     float accelerationRate = 500;
     float decelerationRate = -100;
     float brakeSpeed = 3500f;
     float gravity = 9.81f;
     float slope = 0;
     public Transform rearWheel;
     public Transform frontWheel;
 
     // Use this for initialization 
     public void Start () {
         GetComponent<Rigidbody2D>().centerOfMass = centerOfMass.transform.localPosition;
         wheelJoints = gameObject.GetComponents<WheelJoint2D>();
         motorBack = wheelJoints[0].motor;
         motorBack = wheelJoints[1].motor;
     }  
 
     //all physics based assignment done here
     public void FixedUpdate(){
         torqueDir = Input.GetAxis("Horizontal");
         if(torqueDir!=0){ 
             GetComponent<Rigidbody2D>().AddTorque(3*Mathf.PI*torqueDir, ForceMode2D.Force);
         } 
         else{
             GetComponent<Rigidbody2D>().AddTorque(0);
         }
             
         slope = transform.localEulerAngles.z;
 
         if(slope>=180)
             slope = slope - 360;
         dir = Input.GetAxis("Horizontal"); 
 
         if(dir!=0)
             motorBack.motorSpeed = Mathf.Clamp(motorBack.motorSpeed -(dir*accelerationRate - gravity*Mathf.Sin((slope * Mathf.PI)/180)*80 )*Time.deltaTime, maxFwdSpeed, maxBwdSpeed);
     
         if((dir==0 && motorBack.motorSpeed < 0 ) ||(dir==0 && motorBack.motorSpeed==0 && slope < 0)){
             motorBack.motorSpeed = Mathf.Clamp(motorBack.motorSpeed - (decelerationRate - gravity*Mathf.Sin((slope * Mathf.PI)/180)*80)*Time.deltaTime, maxFwdSpeed, 0);
         }
         else if((dir==0 && motorBack.motorSpeed > 0 )||(dir==0 && motorBack.motorSpeed==0 && slope > 0)){
             motorBack.motorSpeed = Mathf.Clamp(motorBack.motorSpeed -(-decelerationRate - gravity*Mathf.Sin((slope * Mathf.PI)/180)*80)*Time.deltaTime, 0, maxBwdSpeed);
         }
 
 
 
 
         if (Input.GetKey(KeyCode.Space) && motorBack.motorSpeed > 0){
             motorBack.motorSpeed = Mathf.Clamp(motorBack.motorSpeed - brakeSpeed*Time.deltaTime, 0, maxBwdSpeed); 
         }
         else if(Input.GetKey(KeyCode.Space) && motorBack.motorSpeed < 0){ 
             motorBack.motorSpeed = Mathf.Clamp(motorBack.motorSpeed + brakeSpeed*Time.deltaTime, maxFwdSpeed, 0);
         }
         wheelJoints[0].motor = motorBack;
         wheelJoints[1].motor = motorBack;
 
     }
 }