[4.6 GUI] Displaying my pause menu when ESC is pressed

EDITED QUESTION
I have a script, in which i’ve layed out what i think would be the logical order of things that would need to happen when creating a pause menu.
My question is, once the user presses ESC, how do I display the GUI Panel that i’ve already created using the new UI system. This Panel exists in a canvas which I made in another scene.

Thank you for any help! Even pointing me towards the right set of documentation.
-Jon

using UnityEngine;
using System.Collections;

public class InGameGUI : MonoBehaviour {

    private string GUImode = "gaming";

	// Use this for initialization
	void Start () 
    {
	
	}
	
	// Update is called once per frame
	void Update () 
    {
	    if(Input.GetKeyDown("escape")) //Pause game when escape is pressed
        {
            Time.timeScale = 0;
            GUImode = "paused";
        }
	}

    public void DisplayMenu()
    {
        if(GUImode == "paused")
        {
            //display pause menu here

            if(Input.GetKeyDown("escape")) //if escape is pressed to resume game
            {                
                Time.timeScale = 1;
                GUImode = "gaming";
            }
            if(/*add condition for when game is quit*/) //If quit button is pressed return to main menu
            {
                Time.timeScale = 1;
                GUImode = "quitting";
                Application.LoadLevel("MainMenu");
            }
        }
    }
}

The UI system and OnGUI are completely separate systems, and should not be used together.

Move all of your OnGUI code to Update. Create a GameObject variable to store the panel. Use SetActive() to turn it on and off.

You call GUI methods, like GUI.DrawTexture, GUI.BOX, etc… Here is a link to a thread having almost same matter: Making a GUI panel appear on boolean true - Unity Answers