How to extend a selfmade controller?

[eluser]kevinh21[/eluser]
Hi everyone
I made a main controller that is used to build the website and handling errors and some things...it's called wsite Controller.

Now, i would like to "link" all my new controllers to this controller instead of CI's default Controller.

How can i do this?

wsite.php

Code:

<?php
class Wsite extends Controller
{
....
}
?>

blog.php

Code:

<?php
class Blog extends Wsite
{
....
}
?>

Where/how do i have to declare the wsite controller so that the blog controller can extend wsite?