Swich fire button form F to LMB

in this script the fire button is on F but i want it on LMB but i dont know how. can somone helt me pliz?

     var Range : float = 1000;
     
     var Force : float = 1000;
     
     var Clips : int = 20;
     
     var BulletPerClip : int = 60;
     
     var RelaodTime : float = 3.3;
     
        var Damage : int = 10;
        
     var MoveSpeed: float = 1;
     
         var BulletsLeft : int = 0;
         
             var ShootTimer : float = 0;
             
             
             
             var ShootCooler : float = 0.5;
             
             public var ShootAudio : AudioClip;
             
             public var ReloadAudio : AudioClip;
             
             public var muzzleFlash : ParticleEmitter;
             
             public var hitParticles : ParticleEmitter;
             
             public var muzzleFlashTimer : float = 0;
              
             public var KeyCooler : float = 0.5;
             
                public var KeyTimer : float = 0;
             
             public var muzzleFlashCooler : float = 0.5;
             
             public var Lights1 : GameObject;
             
             public var Lights2 : GameObject ;
             
             public var Lights3 : GameObject;
             
             public var BloodEffect : ParticleEmitter;
     
               public var BloodEffectMain: ParticleEmitter;
     
     
     
              //var PlayerPos : Transform;
              //var RadarCam : Transform;
              //    //var Finder: Transform;
              //var CamFinder: Transform;
              
  

function Start(){

// PlayerPos.rotation = Quaternion.Euler(0,96.93118,0); // PlayerPos.position = Finder.position; //RadarCam.position = CamFinder.position;

     BulletsLeft = BulletPerClip;
     
     
     muzzleFlash.emit = false;
     
     
     DefaultPos = transform.localPosition;
     
     hitParticles.emit = false;
     
     BloodEffect.emit = false;
     BloodEffectMain.emit = false;
     
       
  

}

function Update () {

//PlayerPos.rotation = mainPos.rotation; //PlayerPos.position = Finder.position; //RadarCam.position = CamFinder.position;

if( KeyTimer > 0){

  KeyTimer -= Time.deltaTime;
   

}

if( KeyTimer < 0){

  KeyTimer= 0;
   

}

if( muzzleFlashTimer > 0){

  muzzleFlashTimer -= Time.deltaTime;

MuzzleFlash(); }

if( muzzleFlashTimer < 0){

  muzzleFlashTimer = 0;
 

}

if( ShootTimer > 0){

          ShootTimer -= Time.deltaTime;

}

if(ShootTimer < 0){

                ShootTimer = 0;
               
               }
               
          if( KeyTimer == 0){
         if(Input.GetKey(KeyCode.F) && BulletsLeft ){
         
         if( ShootTimer  == 0){
         
         PlayShootAudio();
         
          
             RayShoot();
              
             
                
             ShootTimer  = ShootCooler;
             KeyTimer = KeyCooler;
             
             }
             
                 if( muzzleFlashTimer == 0){
              
               muzzleFlashTimer = muzzleFlashCooler;   
                     MuzzleFlash ();    

}
}

} }

function MuzzleFlash (){

if( muzzleFlashTimer > 0){

     muzzleFlash.emit= false;
        
        Lights1.active = false;
        Lights2.active = false;
        Lights3.active = false;
           

} if( muzzleFlashTimer == muzzleFlashCooler){

   muzzleFlash.transform.localRotation = Quaternion.AngleAxis(Random.value * 360 , Vector3.forward);

      muzzleFlash.emit = true;
        
         Lights1.active = true;
        Lights2.active = true;
        Lights3.active = true;

} }

function RayShoot (){

//GameObject.Find("m1911pistoleReloadandShooting").animation.Play("Shoot"); //(if your player has animations then remove the // infront of the GameObject.Find and then //(replace your objetcs name there. and then the animation name) var hit : RaycastHit;

              var direction : Vector3  = transform.TransformDirection(Vector3.forward);
      
             Debug.DrawRay(transform.position , direction * Range , Color.blue);
             
             if(Physics.Raycast(transform.position , direction , hit, Range)){
             var hitRotation = Quaternion.FromToRotation(Vector3.up, hit.normal);
             
             if(hit.rigidbody){
             
             if(hitParticles){
             
             hitParticles.transform.position = hit.point;
             
             hitParticles.transform.localRotation = Quaternion.FromToRotation(Vector3.up, hit.normal);
             hitParticles.Emit();

                        
             hit.rigidbody.AddForceAtPosition( direction * Force , hit.point);
             hit.collider.SendMessageUpwards("ApplyDamage" , Damage , SendMessageOptions.DontRequireReceiver);
             }
             }
             
             if(hit.collider.gameObject.CompareTag("Enemy")){
             
                 if( BloodEffect ){
                 if( BloodEffectMain){
                 
                 BloodEffect.transform.position = hit.point;
                 BloodEffect.transform.position = hit.point;
                 
                 BloodEffect.transform.localRotation = Quaternion.FromToRotation(Vector3.forward, hit.normal);
                 BloodEffectMain.transform.localRotation = Quaternion.FromToRotation(Vector3.forward, hit.normal);
                 BloodEffect.Emit();
                 BloodEffectMain.Emit();
                 
             }
             }
             }
             }
             
             
             
             
             BulletsLeft --;
              
         
             if(BulletsLeft < 0){
             
             BulletsLeft = 0;
             
             }
             
             if( BulletsLeft == 0 ){
             
             Reload();
             
             
             }

             }
 

function Reload (){

     PlayReloadAudio();
     yield WaitForSeconds(0.2);
     
      //GameObject.Find("m1911pistoleReloadandShooting").animation.Play("Reload"); //(if your player has animations then remove the // infront of the GameObject.Find and then 
                                                                                      //(replace your objetcs name there. and then the animation name)
  yield WaitForSeconds( RelaodTime);
  
          if(Clips > 0){
          
             BulletsLeft = BulletPerClip; 
             
                        Clips -= 1;           
          

} }

function PlayShootAudio(){

     audio.PlayOneShot( ShootAudio);

}

function PlayReloadAudio(){

audio.PlayOneShot( ReloadAudio);

}

thanks