[Plugin: Smarter Navigation] How to add to my template?

Hy. I use the arjuna template (http://wordpress.org/extend/themes/arjuna-x ). In the single.php i have:
<?php arjuna_get_post_pagination(__('Previous Page', 'Arjuna'), __('Next Page', 'Arjuna'));?>. In the functions.php file i have:

function arjuna_get_previous_post_link($label) {

	$post = get_adjacent_post(false, '', true);

	if (!$post) return;

	echo '<a href="'.get_permalink($post).'" rel="prev" class="newer"><span>'.$label.'</span></a>';

}

What and where to change to make it work? Thank you.

http://wordpress.org/extend/plugins/smarter-navigation/