Accessing a button in C# script

Unity Engine
1

I added a button to a canvas in unity and I want to change its text on a different button click. How do I access a buttons text property in code?? Thanks for the help!

2 
using UnityEngine;
using UnityEngine.UI;
using System.Collections;

public class ChangeButtonText : MonoBehaviour {

    public Button btn = null;

    public void changeText(string newText)
    {
        btn.GetComponentInChildren<Text>().text = newText;
    }
}