Enqueue stylesheet for admin area Add to functions.php

enqueue-admin-stylesheet.php

      // Enqueue stylesheet for admin area
      add_action( 'admin_enqueue_scripts', 'load_admin_style' );
      function load_admin_style() {
        wp_enqueue_style( 'admin_css', get_template_directory_uri() . '/admin.css', false, '1.0.0' );
       }