example only – there will be many more different ways to do this.
– in functions.php of a child theme, add the necessary code to create a new widget area; example:
add_action( 'after_setup_theme', 'twentyfifteenchild_setup' );
function twentyfifteenchild_setup() {
add_action( 'widgets_init', 'twentyfifteenchild_widgets_init' );
add_filter( 'body_class', 'twentyfifteenchild_body_class' );
}
//register right sidebar
function twentyfifteenchild_widgets_init() {
register_sidebar( array(
'name' => __( 'Right Sidebar Widget Area', 'twentyfifteen' ),
'id' => 'right',
'description' => __( 'Add widgets here to appear in your right sidebar.', 'twentyfifteen' ),
'before_widget' => '<aside id="%1$s" class="widget %2$s">',
'after_widget' => '</aside>',
'before_title' => '<h2 class="widget-title">',
'after_title' => '</h2>',
) );
}
//body class correction
function twentyfifteenchild_body_class( $classes ) {
if ( is_active_sidebar( 'right' ) ) {
$classes[] = 'two-sidebars';
}
return $classes;
}
– (one possibility) at the start of footer.php of the child theme, call a new sidebar (this way the right sidebar is available with all template files); example:
<?php get_sidebar( 'right' ); ?>
– create a file sidebar-right.php in the child theme, with this code:
<?php
/**
* The sidebar containing the right widget area - child theme
*
* @package WordPress
* @subpackage Twenty_Fifteen
* @since Twenty Fifteen 1.0
*/
if ( is_active_sidebar( 'right' ) ) : ?>
<div id="sidebar-right" class="sidebar-right">
<div id="tertiary" class="tertiary">
<div id="widget-area" class="widget-area" role="complementary">
<?php dynamic_sidebar( 'right' ); ?>
</div><!-- .widget-area -->
</div><!-- .tertiary -->
</div><!-- .sidebar-right -->
<?php endif; ?>
– add some corrresponding CSS to style.css of the child theme … possibly with @media queries to adjust the layout to narrow screens.
full child theme example code: http://www.transformationpowertools.com/wordpress/wp-content/uploads/2015/07/twentyfifteen-ts.zip
