Jose Castaneda on "Replace Footer Credits or Add Copyright Text"

Awesome! Since you already have a child theme you can create a new footer.php file.

What's nice is that WordPress will use that file instead of the parent's footer file. So what you can do is add the proper lines in the footer. In your case it would be something like:

</div><!-- .body -->
</div><!-- .wrapper -->
<div class="footer">My credit line here &copy; <?php echo date( 'Y' ); ?></div>
<?php wp_footer(); ?>
</body>
</html>

Just make sure that the CSS you used to hide/remove that line gets deleted so it shows back up again. :)