An object reference is required for non-static field, method, or property

I started to making my own game. I found the moving script tutorial for unity 4. But I have unity 5. And I got this error in the following script. Please, help me?

using UnityEngine;
using System.Collections;

public class ControllScript : MonoBehaviour
{
    public float maxSpeed = 10f;
    private bool isFacingRight = true;
    private Animator anim;

	private void Start()
    {
        anim = GetComponent<Animator>();
    }

    private void FixedUpdate()
    {
      
        float move = Input.GetAxis("Horizontal");
        anim.SetFloat("Speed", Mathf.Abs(move));

        rigidbody2D.velocity = new Vector2(move * maxSpeed, rigidbody2D.velocity.y);
      
        if (move > 0 && !isFacingRight)
            Flip();
   
        else if (move < 0 && isFacingRight)
            Flip();
    }

  
    private void Flip()
    {
       
        isFacingRight = !isFacingRight;
       
        Vector3 theScale = transform.localScale;
      
        theScale.x *= -1;
      
        transform.localScale = theScale;
    }
}

rigidbody2D.velocity = new Vector2(move * maxSpeed, rigidbody2D.velocity.y);

You can’t use rigidbody2D like this any more. You need to do the same like for the Animator component: Add a variable to the class the get the component in Start()

private RigidBody2D rigidbody2D;
***
rigidbody2D = GetComponent<RigidBody2D>();