How to display post excerpts on index page on wordpress

Hi Guys,
I'm using free theme for my blog (http://healthluv.com). My problem is this theme display full blog post on home page which cause slow page loading.
So I want to display to excerpts instead of full blog post on index page. Like Title first, then litter descrption and then read more link. But not sure how to do it.
I've read other solutions as well, which suggests to replace "< ?php the_content(); ?>" with "< ?php the_excerpt(); ?>" in index.php file, but I'm not seeing "< ?php the_content(); ?>" in index file.
Following is the coding in "index.php" file of my theme. Please let me know what changes should I make to see my desired result.
<?php get_header(); ?>
<div id="content" class="clearfix">
<div id="main" class="col620 clearfix" role="main">
<?php if ( have_posts() ) : ?>
<?php /* Start the Loop */ ?>
<?php while ( have_posts() ) : the_post(); ?>
<?php
/* Include the Post-Format-specific template for the content.
* If you want to overload this in a child theme then include a file
* called content-___.php (where ___ is the Post Format name) and that will be used instead.
*/
get_template_part( 'content', get_post_format() );
?>
<?php endwhile; ?>
<?php if (function_exists("diginews_pagination")) {
diginews_pagination();
} elseif (function_exists("diginews_content_nav")) {
diginews_content_nav( 'nav-below' );
}?>
<?php else : ?>
<article id="post-0" class="post no-results not-found">
<header class="entry-header">
<h1 class="entry-title"><?php _e( 'Nothing Found', 'diginews' ); ?></h1>
</header><!-- .entry-header -->
<div class="entry-content">
<p><?php _e( 'It seems we can’t find what you’re looking for. Perhaps searching can help.', 'diginews' ); ?></p>
<?php get_search_form(); ?>
</div><!-- .entry-content -->
</article><!-- #post-0 -->
<?php endif; ?>
</div> <!-- end #main -->
<?php get_sidebar(); ?>
</div> <!-- end #content -->
<?php get_footer(); ?>
I'll really appreciate your help.

 

you should look for "< ?php the_content(); ?> " in the single.php or "post-single.php" located in your theme directory.

 

See if there is a file called "content.php" in your theme folder. If this file exists open it and replace <?php the_content(); ... ?> with <?php the_excerpt(); ?>