How do I use a GUISkin as a button? C#

using UnityEngine;
using System.Collections;

public class StartUI : MonoBehaviour {

	
	public GUISkin customGUISkin;

	
	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
	
	}
	

	 
	void OnGUI() {
	 
		
	    if (customGUISkin) {
	        Application.LoadLevel("one");
	    }
}
}

My code.

I want it to load level one when you click the customGUISkin but it loads it automatically. Thanks

This explains on what a GUISkin is, how to make one, and how to use GUISkin in script.

using UnityEngine;
using System.Collections;
 
public class StartUI : MonoBehaviour {
    public GUISkin customGUISkin;

    void OnGUI() {
        if( customGUISkin ) {
            GUI.skin = customGUISkin; 
        }

        if (GUILayout.Button("Load")) {
            Application.LoadLevel("one");
        }
    }
}