call a another scripts function from a prefab

When I try to assign an object with the proper script, it won't allow me to add it to the prefab (I even tried to link to link before it was a prefab) unless the game object i'm linking is itself a prefab

this is causing a problem because the function only runs on the clone, not the prefab

SCRIPT B

 ![using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
 
 public class CardStats : MonoBehaviour
 
 {
 
     public Deck deck;
 
     public int cardCost;
     public int cardHealth;
     public int cardDefense;
 
     public Text cardHealthText;
     public Text cardCostText;
     public Text cardDefenseText;
 
     public int cardID;
 
 
     // Use this for initialization
     void Start ()
     {
         
 
         
     }
     
     // Update is called once per frame
     void Update ()
     {
 
         if (cardCost <= 0)
         {
             cardCost = 0;
         }
         if (cardHealth <= 0)
         {
            cardHealth = 0;
         }
         if (cardDefense <= 0)
         { 
             cardDefense = 0;
         }
 
 
         if (Input.GetKeyDown(KeyCode.D))
         {
 
 
             cardID = deck.tempDeck[0];
            
             Debug.Log(" Huh? " + cardID);][1]

[1]: /storage/temp/94415-deck-snip-1.png