The template system allows you to overwrite the related posts HTML. By default, the plugin will load it’s own template file that is included in the plugin. This template file can be found in the templates folder in the Related Posts for WordPress Premium directory. If you would like to change one of the template files, simply copy the file to your WordPress theme in the directory related-posts-for-wp. This directory probably doesn’t exists yet, if this is the case simply create the directory. After you’ve copied the template file to your WordPress theme, the plugin will automatically load the template file in your WordPress theme.
Please note that you should not change the template files located in the plugin folder, all changes done in these files will be lost when you update the plugin.