Adding a non-administrative menu

Hello to all,
I created an eCommerce plugin to embed in a WordPress platform. I succeded adding a menu to the control panel, but only administrators can view it; I have to make the menu viewable by all the users. How can obtain it? Here is the code:

add_action('admin_menu', 'mrt_add_menu');

function mrt_add_menu() {
   add_menu_page('Carrello Elettronico', 'Carrello Elettronico', 8, __FILE__, 'mrt_sms_main_control');
   add_submenu_page(__FILE__, 'Carica prodotto', 'Carica prodotto', 8, 'Carica prodotto', 'carico_prodotti');
   add_submenu_page(__FILE__, 'Utenti', 'Utenti', 8, 'Utenti', 'utenti');
   add_submenu_page(__FILE__, 'Visualizzazione esterna', 'Visualizzazione esterna', 8, 'Visualizzazione esterna', 'visualizza');
   add_submenu_page(__FILE__, 'Opzioni', 'Opzioni', 8, 'Subscribers', 'mrt_sms_subscribers_page');
   add_submenu_page(__FILE__, 'Support', 'Support', 8, 'Support', 'mrt_sms_support_page');
}