register_sidebar notice [closed]

1. Find file where is register_sidebar ( must be on theme folder or plugins )

2. add ID to sidebar

   register_sidebar( array(
      'name' => __( 'Main Sidebar', 'theme-slug' ),
   
      'id' => 'change_me',  // Add only this line
   
      'description' => __( 'Widgets in this area will be shown on all posts and pages.', 'theme-slug' ),
      'before_widget' => '<li id="%1$s" class="widget %2$s">',
      'after_widget'  => '</li>',
      'before_title'  => '<h2 class="widgettitle">',
      'after_title'   => '</h2>',
    ) );
   

Or you can just disable notification in wp-config.php

edit WP_DEBUG to false

define('WP_DEBUG', false);