Theme developement – incative sidebars

Change 'id' => 'sidebar-1', as your own sidebar name. For example, new sidebar name is sidebar-2 than, our function will –

add_action( 'widgets_init', 'theme_slug_widgets_init' );

    function twentyfifteen_widgets_init() {
    register_sidebar( array(
        'name'          => __( 'Widget Area', 'twentyfifteen' ),
        'id'            => 'sidebar-2',
        'description'   => __( 'Add widgets here to appear in your sidebar.', 'twentyfifteen' ),
        'before_widget' => '<aside id="%1$s" class="widget %2$s">',
        'after_widget'  => '</aside>',
        'before_title'  => '<h2 class="widget-title">',
        'after_title'   => '</h2>',
    ) );
}
add_action( 'widgets_init', 'twentyfifteen_widgets_init' );

`