How to controlling an object using built-in button?

need help guys...

i already create a character that can move and jump by following some unity tutorial... but how to change the control button from keyboard (like up, down, left, & right) to built-in button?

it's really confusing, do i need to pass the value from script on the button to the script on the character? or what should i do exactly to be able controlling the character with built-in button?

this is the script for moving my character, i simply follow this tutorial to do that

void FixedUpdate () {

     move = Input.GetAxis ("Horizontal");
     
     grounded = Physics2D.OverlapCircle (groundCheck.position, groundRadius, whatIsGround);
     anim.SetBool ("Ground", grounded);
     
     anim.SetFloat ("vSpeed", rigidbody2D.velocity.y);

     
     if (grounded)
         loncat = false;
     
     anim.SetFloat ("Speed", Mathf.Abs(move));
     
     rigidbody2D.velocity = new Vector2 (move * maxSpeed, rigidbody2D.velocity.y);
     
     if (move > 0 && !facingRight) {
         flip();        
     }
     else if(move < 0 && facingRight){
         flip();
     }        
 }

and Thanks before for anybody that willing to help me...