Can't add script behaviour Run.

Hi ! I found a script to make my FPS run for a limited time. The script is correct but i dont understand why i can't put it on my First Person Player. This is the script.

 using UnityEngine;
 using System.Collections;
  
 [RequireComponent(typeof(AudioSource))]
  
 public class RunAndCrouch : MonoBehaviour 
 {
     public float walkSpeed = 7; // regular speed
     public float crchSpeed = 3; // crouching speed
     public float runSpeed = 20; // run speed
     public float runDuration = 5.0f;
     public float runRegenTime = 15.0f;
 
     private CharacterMotor chMotor;
     private Transform tr;
     private float dist; // distance to ground
  
     bool canRun = true;
     bool tryRun = false;
  
     public AudioClip outOfBreath;
  
     // Use this for initialization
     void Start () 
     {
        ///AUDIO
        if(!GetComponent<AudioSource>())
          gameObject.AddComponent<AudioSource>();
        audio.clip = (AudioClip)outOfBreath;
        audio.loop = false;
        audio.playOnAwake = false;
        ///
         StartCoroutine("CheckRunEnergy");
         chMotor =  GetComponent<CharacterMotor>();
         tr = transform;
         CharacterController ch = GetComponent<CharacterController>();
         dist = ch.height/2; // calculate distance to ground
     }
  
     // Update is called once per frame
     void FixedUpdate ()
     {
        print (canRun);
        float vScale = 1.0f;
         float speed = walkSpeed;
  
         if ((Input.GetKey("left shift") || Input.GetKey("right shift")) && chMotor.grounded)
         {
          tryRun = true;
          if(canRun)
                 speed = runSpeed;
          else if(!canRun)
           speed = walkSpeed;
         }
        else
          tryRun = false;
  
         if (Input.GetKey("c"))
         { // press C to crouch
             vScale = 0.5f;
             speed = crchSpeed; // slow down when crouching
         }
  
         chMotor.movement.maxForwardSpeed = speed; // set max speed
         float ultScale = tr.localScale.y; // crouch/stand up smoothly 
  
        Vector3 tmpScale = tr.localScale;
        Vector3 tmpPosition = tr.position;
  
        tmpScale.y = Mathf.Lerp(tr.localScale.y, vScale, 5 * Time.deltaTime);
        tr.localScale = tmpScale;
  
        tmpPosition.y += dist * (tr.localScale.y - ultScale); // fix vertical position       
        tr.position = tmpPosition;
     }
  
     IEnumerator CheckRunEnergy()
     {
        while(true)
        {
          if(tryRun)
          {
           while(canRun)
           {
               yield return new WaitForSeconds(runDuration);
               canRun = false;
            audio.PlayOneShot(outOfBreath, 1.0f);
           }
           while(!canRun)
           {
               yield return new WaitForSeconds(runRegenTime);
               canRun = true;
           }
          }
  
  
          yield return new WaitForEndOfFrame();
        }
     }
 }

Im new on unity and sorry for my bad english.