How tto add dividing line between posts?

Is it possible to see the posts’ web page in order to help suggesting the appropriate solution?

yes

https://spinningarrow.org/stitch/

I would like to have it separate kinda like in this page https://squattheplanet.com/

Probably the easiest way would be editing your style sheet.

Look for this

.post {
...
}

Add this in between the { }
border-bottom: 1px solid #999999;

You can also play around with the values and get whatever you like.
Resource:
https://www.w3schools.com/css/css_border.asp

Thanks is working now!

And if your (or others) template does not include a defined style for Post (like mine,) you can add a fixed separator within the main index template, which will look something like this depending on your template:

<?php get_header(); ?>
<div id=”content”>
<?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post(); ?>
<div class=”entry”>
<div class=”post” id=”post-<?php the_ID(); ?>”>
<h2>” rel=”bookmark” title=”Permanent Link to <?php the_title(); ?>”><?php the_title(); ?></h2>
<small><?php the_time(‘F jS, Y’) ?> <!– by <?php the_author() ?> –> Posted in <?php the_category(‘, ‘) ?> | <?php edit_post_link(‘Edit’, ”, ‘ | ‘); ?> <?php comments_popup_link(‘No Comments »’, ‘1 Comment »’, ‘% Comments »’); ?></small>
<?php the_content(‘Read the rest of this entry »’); ?>
<!– place your separator between –>
<div style=”border-bottom: 1px solid #333333″></div>
<!– or –>
<HR>
<!– place your separator between –>
</div>
</div>