Need help with error: an object reference is required to access non-static member

Unity is brand new to me and I began by following the video tutorials for making a roll ball game. I made it to the third video where he goes through writing the script to get the ball to move. I followed his exact steps but i keep getting the error in the title of this thread. This is my script for the ball control. Any help is greatly appreciated, thank you.

usingUnityEngine;
usingSystem.Collections;

using UnityEngine;
using System.Collections;

public class PlayerController : MonoBehaviour
{
    void FixedUpdate ()
    {
        float moveHorizontal = Input.GetAxis ("Horizontal");
        float moveVertical = Input.GetAxis ("Vertical");

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

        Rigidbody.AddForce(movement);
    }
}

lol thank you