How do I get a character to move (Without the default scripts, which don't seem to work)?

I'm basically making a test/joke game, so I don't care about the details too much, just want to make something actually happen. This is my first time trying to use Unity. The character is a rectangular prism with no animations. I have a rigidbody, a box collider, and the script "moving better hopefully", which I found online (I named it though)

using UnityEngine; using System.Collections;

public class movingBetterHopefully : MonoBehaviour {

 public float speed;
 
 private Rigidbody rb;
 
 void Start ()
 {
     rb = GetComponent<Rigidbody> ();
 }
 
 void FixedUpdate ()
 {
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical");
     
     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
     
     rb.AddForce (movement * speed);
 }

}

(Sorry for the formatting...)

I can set the inputs when I build the game, but the character can't actually move. What do I need to do here? Thanks in advance, and sorry for being pretty ignorant about the whole process... I've been trying to get this working for probably a week now and getting pretty frustrated.