Register widget area for newsletter section.

functions.php

<?php
// Do NOT include the opening php tag.

// Register Newsletter widget area.
genesis_register_sidebar( array(
	'id'          => 'newsletter',
	'name'        => __( 'Newsletter', 'theme-name' ),
	'description' => __( 'This is the newsletter widget area.', 'theme-name' ),
) );