Passing the Google Structured Data Testing Tool

I was checking my site for correctly coded structured data and I get this error in Google Webmaster Tools. The tips on the web ask you to edit a line in single.php (which doesn’t exist in Customizr afaik) and my site is largely made of Pages.

One advice is as follows:

Fix Missing required field “updated”

look for the code below on your WordPress theme’s single.php file.
001 <span class=”post_date”><?php the_time(‘j F,Y’); ?></span>

then add “date updated” attribute to it. Your code should look like
001 <span class=”post_date date updated”><?php the_time(‘j F,Y’); ?></span>

and

Fix Warning: Missing required hCard “author” and Missing required field “name (fn)”

This will fix these 2 warnings. On your WordPress theme’s single.php file, look for
001 <span class="theauthor"><?php the_author_posts_link(); ?></span>

or
001 <span class="theauthor"><?php the_author(); ?></span>

replace it with

001	<span class="vcard author">
002	<span class="fn"><?php the_author_posts_link(); ?></span>
003	</span>

or

001	<span class="vcard author">
002	<span class="fn"><?php the_author(); ?></span>
003	</span>

Where can I do this?