How do you make your player jump in the Roll-a-Ball tutorial series?

Okay so I was wondering if there was a way to make your player bounce up (jump) in the Roll-a-Ball tutorial series. Can someone write out a C# script for me on how to jump up and go back down on the ground without having the ability to jump multiple times. I am super new to this scripting stuff so if anybody could make it easy for me I would very much appreciate that (please). Thanks!

This is what the player script looks like :

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

public class PlayerController : MonoBehaviour {

 public float speed;
 public Text countText;
 public Text winText;

 private Rigidbody rb;
 private int count;

 void Start ()
 {
     rb = GetComponent<Rigidbody>();
     count = 0;
     SetCountText ();
     winText.text = "";
 }

 void FixedUpdate ()
 {
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical");

     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

     rb.AddForce (movement * speed);
 }

 void OnTriggerEnter(Collider other) 
 {
     if (other.gameObject.CompareTag ( "Pick Up"))
     {
         other.gameObject.SetActive (false);
         count = count + 1;
         SetCountText ();
     }
 }

 void SetCountText ()
 {
     countText.text = "Count: " + count.ToString ();
     if (count >= 12)
     {
         winText.text = "You Win!";
     }
 }

}