C# Hazır yapılan programa buton nasıl eklenir?

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class PlayerController : MonoBehaviour.
{
 public static PlayerController instance;

 public float moveSpeed;
 private Vector2 moveInput;

 public Rigidbody2D theRB;

 public Transform gunArm;

 //private Camera theCam;

 public Animator anim;

 /* public GameObject bulletToFire;
 public Transform firePoint;

 public float timeBetweenShots;
 private float shotCounter; */

 public SpriteRenderer bodySR;

 private float activeMoveSpeed;
 public float dashSpeed = 8f, dashLength = .5f, dashCooldown = 1f, dashInvincibility = .5f;
 [HideInInspector]
 public float dashCounter;
 private float dashCoolCounter;

 [HideInInspector]
 public bool canMove = true;

 public List<Gun> availableGuns = new List<Gun>();
 [HideInInspector]
 public int currentGun;

 // Joystick.
 [SerializeField] private FixedJoystick fixedJoystick;

 private void Awake()
 {
 instance = this;
 DontDestroyOnLoad(gameObject);
 }

 // Start is called before the first frame update.
 void Start()
 {
 activeMoveSpeed = moveSpeed;

 UIController.instance.currentGun.sprite = availableGuns[currentGun].gunUI;
 UIController.instance.gunText.text = availableGuns[currentGun].weaponName;

 }

 // Update is called once per frame.
 void Update()
 {
 if (canMove && !LevelManager.instance.isPaused)
 {
 // Klavye girişlerini al.
 moveInput.x = Input.GetAxisRaw("Horizontal");
 moveInput.y = Input.GetAxisRaw("Vertical");

 // Joystick girişlerini ekle.
 moveInput.x += fixedJoystick.Horizontal;
 moveInput.y += fixedJoystick.Vertical;

 moveInput.Normalize();

 theRB.velocity = moveInput * activeMoveSpeed;

 Vector3 mousePos = Input.mousePosition;
 Vector3 screenPoint = CameraController.instance.mainCamera.WorldToScreenPoint(transform.localPosition);

 if (mousePos.x < screenPoint.x)
 {
 transform.localScale = new Vector3(-1f, 1f, 1f);
 gunArm.localScale = new Vector3(-1f, -1f, 1f);
 }
 else.
 {
 transform.localScale = Vector3.one;
 gunArm.localScale = Vector3.one;
 }

 Vector2 offset = new Vector2(mousePos.x - screenPoint.x, mousePos.y - screenPoint.y);
 float angle = Mathf.Atan2(offset.y, offset.x) * Mathf.Rad2Deg;
 gunArm.rotation = Quaternion.Euler(0, 0, angle);

 if (Input.GetKeyDown(KeyCode.Tab))
 {
 if (availableGuns.Count > 0)
 {
 currentGun++;
 if (currentGun >= availableGuns.Count)
 {
 currentGun = 0;
 }

 SwitchGun();
 }
 else.
 {
 Debug.LogError("Player has no guns!");
 }
 }

 if (Input.GetKeyDown(KeyCode.Space))
 {
 if (dashCoolCounter <= 0 && dashCounter <= 0)
 {
 activeMoveSpeed = dashSpeed;
 dashCounter = dashLength;

 anim.SetTrigger("dash");

 PlayerHealthController.instance.MakeInvincible(dashInvincibility);

 AudioManager.instance.PlaySFX(8);
 }
 }

 if (dashCounter > 0)
 {
 dashCounter -= Time.deltaTime;
 if (dashCounter <= 0)
 {
 activeMoveSpeed = moveSpeed;
 dashCoolCounter = dashCooldown;
 }
 }

 if (dashCoolCounter > 0)
 {
 dashCoolCounter -= Time.deltaTime;
 }

 if (moveInput != Vector2.zero)
 {
 anim.SetBool("isMoving", true);
 }
 else.
 {
 anim.SetBool("isMoving", false);
 }
 }
 else.
 {
 theRB.velocity = Vector2.zero;
 anim.SetBool("isMoving", false);
 }
 }

 public void SwitchGun()
 {
 foreach (Gun theGun in availableGuns)
 {
 theGun.gameObject.SetActive(false);
 }

 availableGuns[currentGun].gameObject.SetActive(true);

 UIController.instance.currentGun.sprite = availableGuns[currentGun].gunUI;
 UIController.instance.gunText.text = availableGuns[currentGun].weaponName;

 AudioManager.instance.PlaySFX(6);
 }
}