Using Namespaces?

I am stuck. I need to know how I should create a namespace of my own and use it in another script. How would I do this?

Here is a simplification of what I have that doesn't work.

 //script a:
 using UnityEngine;
 using System.Collections;
 
 namespace Enemy {
      public class EnemyController : MonoBehaviour {
           string name;
      }
 }
 
 
 //script b:
 using UnityEngine;
 using System.Collections;
 using Enemy;
 
 public class AI : MonoBehaviour {
      EnemyController enem;
      enem.name = "geoff";
 }