How to make character move faster/slowly? (Noobie question)

Hi! I am pretty new to coding, and I have a simple question (I hope), my code is below and what should I change to make the character goes up faster or down faster? (The code is commented but still no help)

using UnityEngine; using System.Collections;

public class PlayerMovingScript : MonoBehaviour {

 Vector3 velocity = Vector3.zero;                            //Moving vector
 public Vector3 gravity;                                        //How fast the player will fall down
 public Vector3 upVelocity;                                    //How much the player will rise

 public float maxSpeed = 1f;                                    //How fast the player fill rise

 public Animation anim;                                        //Player jump animation

 public AudioSource jump;                                    //Jump sounds

 public static bool startUp;                                    //If player jumps
 public bool didUp = false;                                    //If player jumped


 void FixedUpdate () {
     velocity += gravity * Time.deltaTime;                            //Makes player to fall
     if (didUp == true) {                                            //If player jumped
         didUp = false;                                                //Disables bool
         if (gameObject.transform.position.y <= 11) {                //If player height is lower than the screen can see
             velocity += upVelocity;                                    //Player jump
         }
     }
     velocity = Vector3.ClampMagnitude (velocity, maxSpeed);            //Player rise smoothly
     transform.position += velocity * Time.deltaTime;                //