Open up a dialogue window via right click

What I want to do is when you right click on a selection, instantiated from a prefab and list, it will bring up a window and ask if you want to do a certain action, then click yes or no buttons.
No matter what I do, I can’t seem to get a reference. I thought if I moved the open window script to its own script, that would fix it, only it still says unassigned reference or null reference.

Scripts:

public Canvas DialogueCanvas;
	public bool windowOpen=false;
	public bool DialogueOpen=false;


	public void OpenDialogWindow()
	{

		if(windowOpen==false)
		{
			windowOpen=true;
			DialogueCanvas.enabled = true;


		}
		else if(windowOpen==true)
		{

			windowOpen=false;
			DialogueCanvas.enabled=false;

		}
	}

This is attached to the dialogue canvas

	public Canvas DialogueCanvas;
	public DialogueWindow DW;

public void ClickRight()
	{
		//DBIndexList.Clear ();
		Debug.Log ("You clicked Right!");
		DW = DialogueCanvas.GetComponent<DialogueWindow> ();
		DW.OpenDialogWindow ();
	
	}

This is attached to the prefab.

When I try to drag the canvas over, it won’t let me attach it.
Where am I going wrong? Since this is a delete operation, I’d like to have a dialogue, just in case.
Thanks guys!

I Advise you to not make a Canvas but to Make Panels, but if u stick to canvas do the folliwing.

public GameObject DialogueCanvas;

int latter in your code :

DailogueCanvas.setactive(true);

So you attach gameobjects not Canvas panel etc when u want to active and disable a text, a panel, an image a Canvas etc…

and use this setactive function