How to make an Instantiated prefab a Child of a gameobject that already exists in the hierarchy

I have a script which will Instantiate prefabs which works fine but I wanted them to be added to a gameobject that already exists and make the instantiated prefab a child of the already existing gameobject without making a new one. If it helps here is the script…

	if (randomizer == 1 && i <= 0)
		Instantiate(A, new Vector3 (0,0,0), Quaternion.identity);
		System.Random random = new System.Random();
		randomizer = random.Next (1,5);

and an image of what gameobject I want the Instantiated objects to become children of. Thank you in advance and thank you for helping me with my studies. 18737-untitled-1.jpg

If I understand your question correctly, you can replace line 3 with these two lines:

GameObject go = Instantiate(A, new Vector3 (0,0,0), Quaternion.identity) as GameObject; 
go.transform.parent = GameObject.Find("Stage Scroll").transform;

Instantiate has several acceptations and a couple of them already accept the Transform element which will become the parent of the instantiate object, check the documentation:

it has random position when instatianted lik -5.51 1.26 -35.37 how do i make it 0,0,0?