Working with menus

How to add a item in main menu for add content

/**
* Implements hook_menu_alter().
*/
function reserva_sala_menu_alter(&$items) {

$items['node/add/reserva']['title'] = 'Reservar';
$items['node/add/reserva']['description'] = 'Reservar';
$items['node/add/reserva']['menu_name'] = 'main-menu';
$items['node/add/reserva']['type'] = MENU_NORMAL_ITEM;

}