How to "pop balloons"?

If you are new to Unity, which I am guessing you are since Instantiate (what you could use for adding a prefab to the world) is one of the first methods you will learn about, I suggest starting with some of the tutorials. They will introduce you to the basic programming concepts and how to apply them in Unity. Unity's own tutorials are some of the best. Start here: https://unity3d.com/learn/tutorials

I suggest doing the 2D UFO tutorial. It will introduce some of the concepts you need to do what you are trying to.

Once you go through a few of those, you should be able to figure this out. To pop ballons on click, you will probably just need to learn about this method: https://docs.unity3d.com/ScriptReference/MonoBehaviour.OnMouseDown.html