Adding GUI to this

Hi. I watched a YouTube tutorial about random numbers.
But I he didn’t add any GUI text to it. I tried doing it myself, but failed.
What I wanted was a button which you could press. When you pressed the button, you got a random number pops up on the screen.

Here is the script he made:

var randNumber : int;

function Update () {
	if (Input.GetMouseButtonDown(0)) {
		randNumber = Random.Range(1.0, 100.0);
		Debug.Log (randNumber);

How can i make that GUI button thing that I wanted?

That is simple, you need first to study all the links below and I have sure that you will achieve it.