In-App Purchase callbacks code implementation

I'm trying to implement a simple in-app purchase for a non-consumable (unlock level). But, i'm having trouble using the StoreKitManager callbacks from Apple. I'm using the StoreKit from geniteam.

At a certain point in the game a paywall comes up with buttons, one of which, I'm scripting like this:

 void OnClick()
     {
         #if UNITY_IPHONE
         if(StoreKitBinding.canMakePayments() == true)
         {
             Debug.Log("RequestProductData Clicked");            
             
             string[] productIDs = { "com.myAppId.NonConsumable" };
             StoreKitBinding.requestProductData(productIDs);
 
             Debug.Log("MakePurchase Clicked");                
             StoreKitBinding.purchaseProduct("com.myAppId.NonConsumable"); 
         } 
         #endif
     }

The callback from Apple will fire a static public method: StoreKitManager.productsPurchaseSuccessEvent();

The question is how do I handle the static method? Should I put the static method StoreKitManager.productsPurchaseSuccessEvent(); in my game script and access the non-static methods with an instance of the script: GameScript gameScript = new GameScript();

is that the way to go about this???? There is little info out there about how to actually implement code into one's game.

Thanks for any help anyone has to offer.