integrateing landingsite plugin

Hallo,

I am trying to install a landing page plugin ( http://bueltge.de/wp-landingsites-de-plugin/181/)

to my new blog http://www.frank-hamm.webdesign.de


I did the following steps

copied i landingsites_de.php into Plugin-Directory (wp-content/plugins)
copied landingsite.php to atahulpa dirctory

activated the landsite-plugin in admin

so far so good

Now I want to integrate the output to the single articel view

by inserting

<?php include (TEMPLATEPATH . '/landingsite.php'); ?>

IN other Themse this has to be done in single.php, which is not existing in atahulpa.
I think that everything is integrated in the header.php

So my question is:

Where do i have to integrate

<?php include (TEMPLATEPATH . '/landingsite.php'); ?>

in the header.php

to get it displayed under my article in the single view?


Thanks in advance
Frank Hamm