How to put a reference on a prefab through the script ?

Hello,

I pick the same example as this tutorial : Unity - GetComponent

On difference, I add a List<>.

 public class AsecondaryScript : MonoBehaviour
 {
     public int maVariable = 120;
 
     public List<string> testList = new List<string>();
 
     void Start ()
     {
         testList.Add ("Objet A 1");
         testList.Add ("Objet A 2");
         testList.Add ("Objet A 3");
     }
 }

I link this script on a GameObject named : Pair1-1

Next, I put this script on another GameObject named : Pair1-2

 public class AmainScript : MonoBehaviour
 {
     public GameObject otherGameObject;
 
     private AsecondaryScript anotherScript;
 
     void Awake()
     {
         anotherScript = otherGameObject.GetComponent<AsecondaryScript> ();
     }
 
     IEnumerator Start ()
     {
         yield return new WaitForEndOfFrame ();
 
         Debug.Log ("Result 1 : " + anotherScript.maVariable);
         Debug.Log ("Result 2 : " + anotherScript.testList);
         Debug.Log ("Result 3 : ");
 
         foreach(String m in anotherScript.testList)
         {
             Debug.Log( "->" + m);
         }
     }
 }

And finally, I put the reference GameObject Pair1-1 in "OtherGameObject" and it work.

The problem is, if both of my GameObject are Prefabs and are not put in the interface, I can't refer Pair1-1 to Pair1-2.

I need to do it with script.

But how could I do this ?