For https://wordpress.org/support/topic/footer-is-there-a-footer-to-place-a-menu?replies=1

footer.php

<?php
/**
 * The template for displaying the footer
 *
 * Contains the closing of the "site-content" div and all content after.
 *
 * @package WordPress
 * @subpackage Twenty_Fifteen
 * @since Twenty Fifteen 1.0
 */
?>

	</div><!-- .site-content -->
	
	<footer id="colophon" class="site-footer" role="contentinfo">

		
		<?php
		wp_nav_menu( array(
				'menu_class'     => 'cockapoo-footer-menu',
				'theme_location' => 'footer_menu',
				'container_class' => 'cockapoo-footer-menu-container',
			) );
		?>

		<div class="site-info">
			<?php
				/**
				 * Fires before the Twenty Fifteen footer text for footer customization.
				 *
				 * @since Twenty Fifteen 1.0
				 */
				do_action( 'twentyfifteen_credits' );
			?>
			<a href="<?php echo esc_url( __( 'https://wordpress.org/', 'twentyfifteen' ) ); ?>"><?php printf( __( 'Proudly powered by %s', 'twentyfifteen' ), 'WordPress' ); ?></a>

		
		
		</div><!-- .site-info -->
	</footer><!-- .site-footer -->

</div><!-- .site -->

<?php wp_footer(); ?>

</body>
</html>