Where to put do_shortcode

So that will depend on your theme, but using Twenty Fourteen as an example it is pretty easy.

First off you’ll need to use the do_shortcode function, and make sure you call it within the loop.

So the code you’re inserting will look something like this <?php echo do_shortcode('[rt_reading_time label="Reading Time:" postfix="minutes"]'); ?>

That’s what you’ll enter into your theme template. For example, in Twenty Fourteen the post meta is contained in the <div class="entry-meta"></div>. So to get the reading time appended to the end of that, you’ll just add your do_shortcode function into the end of the div. Which will give you this in Twenty Fourteen.

<div class="entry-meta">
	<?php
		if ( 'post' == get_post_type() )
			twentyfourteen_posted_on();

		if ( ! post_password_required() && ( comments_open() || get_comments_number() ) ) :
	?>
	<span class="comments-link"><?php comments_popup_link( __( 'Leave a comment', 'twentyfourteen' ), __( '1 Comment', 'twentyfourteen' ), __( '% Comments', 'twentyfourteen' ) ); ?></span>
	<?php
		endif;

		edit_post_link( __( 'Edit', 'twentyfourteen' ), '<span class="edit-link">', '</span>' );
	?>

	<?php echo do_shortcode('[rt_reading_time label="Reading Time:" postfix="minutes"]'); ?>
</div><!-- .entry-meta -->

That will return a <span> elements containing the reading time wherever you call it in your theme. Then you can wrap it within any elements you want like <div class="your-own-div"><?php echo do_shortcode('[rt_reading_time label="Reading Time:" postfix="minutes"]'); ?></div>.

Within Twenty Fourteen that will look like this.

Hope that helps! Let me know if you have any more questions.