register_sidebar |and| widgets_init

function alpha_sidebar(){
    register_sidebar( array(
	    'name'          => __( 'Single Post Sidebar', 'alpha' ),
	    'id'            => 'sidebar-1',
	    'description'   => __( 'For Single Post Sidebar' ),
	    'before_widget' => '<section id="%1$s" class="widget %2$s">',
	    'after_widget'  => '</section>',
	    'before_title'  => '<h2 class="widgettitle">',
	    'after_title'   => '</h2>',
	));

	register_sidebar( array(
	    'name'          => __( 'Footer Left', 'alpha' ),
	    'id'            => 'footer-left',
	    'description'   => __( 'For Footer Left' ),
	    'before_widget' => '<section id="%1$s" class="widget %2$s">',
	    'after_widget'  => '</section>',
	    'before_title'  => '',
	    'after_title'   => '',
	));

	register_sidebar( array(
	    'name'          => __( 'Footer Right', 'alpha' ),
	    'id'            => 'footer-right',
	    'description'   => __( 'For Footer Right' ),
	    'before_widget' => '<section id="%1$s" class="widget %2$s">',
	    'after_widget'  => '</section>',
	    'before_title'  => '',
	    'after_title'   => '',
	));
}
add_action("widgets_init", "alpha_sidebar");