To check that the code is correctly installed on the website, you should change the following line in the link output code (which you insert on each page of the website)
<?php $client = new BACKLINKS_client(); ?>
to the line
<?php $o = array(); $o['force_show_code'] = true; $client = new BACKLINKS_client($o); ?>
If the commented number or <!--check code--> line does not appear in the page code, then the code is not installed correctly.