Enemy Spawn ??? I want to add a enemy spawn to list when enemy spawn now . help me !!!

void Update()
{
if (Time.time > nextSpawn)
{
nextSpawn = Time.time + spawnRate;
randX = Random.Range(-20, -11);
whereToSpawn = new Vector2(randX, transform.position.y);
Instantiate(EnemySpawer, transform.position, Quaternion.identity);
AddTarget(EnemySpawer.transform);

    }
}
public void AddAllEnemies()
{
    
    foreach (GameObject EnemyL in GameObject.FindGameObjectsWithTag("EnemyL")) ;
    
}
public void AddTarget(Transform EnemySpawer)

{

  enemyList.Add(EnemySpawer);
}

public GameObject enemyPrefab; // connect this in your editor.
List enemies = new List();

void Start ()
{
     // this will call the SpawnEnemy method every 3 seconds.
     // if you want to decrease the time don't do this, but call instead SpawnEnemy in Start and then use at the end of SpawnEnemy:  Invoke ("SpawnEnemy", seconds);

     InvokeRepeating("SpawnEnemy", 3f);
}

void SpawnEnemy ()
{
      // enemyPrefab is your EnemySpawer
     // instantiate return a copy of the instance. so you have to add everytime another object not the same EnemySpawer
     GameObject enemy = Instantiate (enemyPrefab);
     enemy.transform.position = new Vector2( x, y );
     AddEnemy (enemy);
}

void AddEnemy (GameObject enemy)
{
      enemies.Add (enemy);
}