How to make a custom class inherited from Unity's GUI?

Hello, Thank you for taking the time to look at this. The issue I'm having is this:

I'm trying to make my GUI navigable by means of an Xbox controller. To do this I've decided to try making a custom button class that will be inherited from the default Unity GUI.Button class, but hold an extra integer variable that I can assign different buttons so that I may store them in an array, then allow the current one to change based on controller input , etc., etc,

The issue I seem to be having trying to actually do this is that I cannot find (or just lack the knowledge) a way to implement this. I'm not overly familiar with the concept of Inheritance in classes. I've watched a few tutorials for this, and gained some insight on approximately what I need to do, but I'm still a bit fuzzy. I've searched google for a solution to this problem, but to little avail. This appears to be exactly what I need, however I'm having a difficult time understanding what's going on in his code, and how to implement that in such a way that it fits my needs.

This is the code I have created thus far :P, I'm almost certain I'm doing this wrong. Any explanation or help you may be able to provide, I would be greatly appreciative! (If not already apparent, I'm using C#)

 public class CustomButton : GUI {    
 
     public bool Clicked;
     public Rect rect;
     public GUIContent Content;
     public GUIStyle Style;
     public int ButtonID;
 
 
 
         
         
     }