Using RigidBody, how can I make the character move in the direction the camera is facing

I think it may have something to do with Script1 * Script2, however I am not sure.

My two scripts are:

using UnityEngine; using System.Collections;

public class MainPlayer : MonoBehaviour {

 public float speed = 500;
 public float speedAc = 10;
 private Vector3 zeroAc;
 private Vector3 curAc;
 private float sensH = 10;
 private float sensV = 10;
 private float smooth = 0.5f;
 private float GetAxisH = 0;
 private float GetAxisV = 0;

 public GUIText SpeedText;
 
 // Use this for initialization
 void Start () {
     ResetAxes();

     SpeedText.text = speed.ToString();
 }


 void FixedUpdate () {
     
     if (SystemInfo.deviceType == DeviceType.Desktop) {
         float movehorizontal = Input.GetAxis ("Horizontal");
         float movevertical = Input.GetAxis ("Vertical");
         
         Vector3 movement = new Vector3 (movehorizontal, 0.0f, movevertical);
         rigidbody.AddForce (movement * speed * Time.deltaTime);
     }
     else 
     {
         curAc = Vector3.Lerp(curAc, Input.acceleration-zeroAc, Time.deltaTime/smooth);
         GetAxisV = Mathf.Clamp(curAc.y * sensV, -1, 1);
         GetAxisH = Mathf.Clamp(curAc.x * sensH, -1, 1);
         
         Vector3 movement = new Vector3 (GetAxisH, 0.0f, GetAxisV);
         
         rigidbody.AddForce(movement * speedAc);
         
     }
 }

 void ResetAxes(){
     zeroAc = Input.acceleration;
     curAc = Vector3.zero;
 }

}

using UnityEngine; using System.Collections;

public class MainCamera : MonoBehaviour {

 public Transform target;
 public float distance = 10.0f;
 public float sensitivity = 3.0f;
 
 private Vector3 offset; 
 
 void Start ()  {
     offset = (transform.position - target.position).normalized * distance;
     transform.position = target.position + offset;
 }
 
 void Update () {
     Quaternion q = Quaternion.AngleAxis(Input.GetAxis ("CameraRight") * sensitivity, Vector3.up);
     offset = q * offset;
     transform.rotation = q * transform.rotation;
     transform.position = target.position + offset;
 }

}