Help getting a link onto a feature image on wordpress

Please help me, I’m really stuck!

I am trying to edit a theme I downloaded so I can add a custom link to a featured image.
How do I do it? I’ve read about turning on the custom field, but that option is not available on the theme.

This is the area of the theme that controls the testimonials (which has the code for the featured image, but this needs to be a link).

<?php $home_testimonial_count = intval(of_get_option('ttrust_home_testimonials_count')); ?>
<?php if($home_testimonial_count > 0) : ?>
<?php $testimonails_bkg = of_get_option('ttrust_testimonials_bkg'); ?>
<div id="testimonials" class="full homeSection clearfix <?php if($testimonails_bkg) echo "hasBackground"; ?>">
	<?php if(of_get_option('ttrust_testimonials_title') || of_get_option('ttrust_testimonials_description')) : ?>
	<div class="sectionHead">		
	<h3><span><?php echo of_get_option('ttrust_testimonials_title'); ?></span></h3>	
	<p><span><?php echo of_get_option('ttrust_testimonials_description'); ?></span></p>		
	<?php endif; ?>		
	$args = array(
		'ignore_sticky_posts' => 1,    	
    	'post_type' => array(				
		'posts_per_page' => $home_testimonial_count,
	$testimonials = new WP_Query( $args );		
	<div class="wrap">
	<div class="testimonials thumbs clearfix">
		<?php while ($testimonials->have_posts()) : $testimonials->the_post(); ?>			    
		<div <?php post_class('small'); ?>>		
			<div class="inside">		
				<?php the_post_thumbnail("ttrust_square_medium", array('class' => '', 'alt' => ''.get_the_title().'', 'title' => ''.get_the_title().'')); ?>						
				<?php the_content(); ?>	
				<span class="title"><span>- <?php the_title(); ?></span></span>
		<?php endwhile; ?>		
<?php endif; ?>

Now how can I turn the featured image into a link ( a custom link to a specific page! not the testimonial).?

I’ll be soooo grateful if somebody can help me.

couple of ways could be tried.
the image here
with the p=whatever page id number is the page you wish to direct it to.

another way to link images & pages is w/

<a <?php echo get_stylesheet_directory_uri() ?> whatever

<?php get_template_directory_uri(); ?>

I think those might help the third one. the get templage dirctory is better used if you are using a child theme.
hope this helps.