Adding a custom page between the header and footer

[Jago^]

So, i know how to get the tabs working by adding these codes to the index.template.php

Now, i'd like to make the link work so that it loads a page (html) between those tabs and the footer of the forum.
Here it is vaguely explained:
http://www.simplemachines.org/community/index.php?topic=63203.msg502973#msg502973
That doesn't work for me though, i tried adding the codes shown there.

Any idea what should be added to make the custom page load when clicking the tab?

edit:

something like this
(i didn't achieve that, just paint skills ):