Help adding a divider line between posts.

Here are a couple of simple ways to do this.

1. Add a Horizontal Rule <hr> tag at the end of the template
2. Use custom CSS to add a border to the bottom of the ivycat-post class.

   .ivycat-post {
       border-bottom: #EEE 1px solid;
   }

Both of these have the undesirable effect of adding an extra line at the bottom of the list of posts. To keep from doing this, you’ll need to add another block of custom CSS that uses the :last-child pseudo class to remove the bottom border from the last .ivycat-post element. Adding it would look something like the following.

.ivycat-post {
    border-bottom: #EEE 1px solid;
}
.ivycat-post:last-child {
    border-bottom: none;
}

I am a little confused. Should steps 1 and 2 be added to posts_loop_template?

<!-- NOTE: If you need to make changes to this file, copy it to your current theme's main
	directory so your changes won't be overwritten when the plugin is upgraded. -->

<!-- Start of Post Wrap -->
<div class="post hentry ivycat-post clear">

        <!-- This will output of the featured image thumbnail  -->
	<div class="featured-image">
	    <?php the_post_thumbnail( array( 180, 9999 ), array( 'class' => 'alignleft' , 'style' => 'border:5px solid white ; margin-right:5px ;' ) ); ?>
	</div>

	<!-- This is the output of the post TITLE -->
	<h2 class="entry-title"><a>"><?php the_title(); ?></a></h2>

	<!-- This is the output of the META information -->
	<div class="entry-utility">
		<?php if ( count( get_the_category() ) ) : ?>
			<span class="cat-links">
				<?php printf( __( '<span class="%1$s">Posted in</span> %2$s', 'twentyten' ), 'entry-utility-prep entry-utility-prep-cat-links', get_the_category_list( ', ' ) ); ?>
			</span>
			<span class="meta-sep">|</span>
		<?php endif; ?>
		<?php
			$tags_list = get_the_tag_list( '', ', ' );
			if ( $tags_list ):
		?>
			<span class="tag-links">
				<?php printf( __( '<span class="%1$s">Tagged</span> %2$s', 'twentyten' ), 'entry-utility-prep entry-utility-prep-tag-links', $tags_list ); ?>
			</span>
			<span class="meta-sep">|</span>
		<?php endif; ?>
		<span class="comments-link"><?php comments_popup_link( __( 'Leave a comment', 'twentyten' ), __( '1 Comment', 'twentyten' ), __( '% Comments', 'twentyten' ) ); ?></span>
		<?php edit_post_link( __( 'Edit', 'twentyten' ), '<span class="meta-sep">|</span> <span class="edit-link">', '</span>' ); ?>
	</div>

	<!-- This is the output of the EXCERPT -->
	<div class="entry-summary">
		<?php the_excerpt(); ?>
	</div>
</div>
<!-- // End of Post Wrap -->

1 is something you could add to the bottom of the posts_loop_template.

2 is something you would add as custom CSS; probably to a custom CSS field in the back end of your theme.

If you can’t find someplace to add custom css in your theme, you may want to look at a plugin such as Simple Custom CSS or Jetpack’s Custom CSS.