Sidebars

Call register_sidebar() for each sidebar you want to create.

# Define the 'main-sidebar'.
add_action( 'widgets_init', 'my_register_sidebars' );
function my_register_sidebars(){

    register_sidebar(
        array(
            'id' => 'main-sidebar',
            'name' => __( 'Main Sidebar' ),
            'description' => __( 'Widgets in this area will be shown on all posts and pages.' ),
            'before_widget' => '<aside id="%1$s" class="widget %2$s">',
            'after_widget' => '</aside>',
            'before_title' => '<h3>',
            'after_title' => '</h3>'
        )
    );

    /* Repeat register_sidebar() code here for each additional sidebar. */
}