You didn’t mention the theme you are using. I’ll assume you want to remove the link on the post’s title. Go to Appearance -> Editor then edit loop-single.php
Change this line:
<h1 class="entry-title"><a href="<?php the_permalink(); ?>"><?php echo the_title(); ?></a></h1>
To this:
<h1 class="entry-title"><?php echo the_title(); ?></h1>