run site on /admin url code example
Example: wordpress admin url
<?php
echo '<a href="' . esc_url( admin_url('nav-menus.php') ) . '">' . esc_html( 'Add Menu' ) . '</a>';
?>
<?php
echo '<a href="' . esc_url( admin_url('nav-menus.php') ) . '">' . esc_html( 'Add Menu' ) . '</a>';
?>