Create submenu

Hello everybody, exuce me for a stupid question, but i can’t create a submenu in Posts menu, can somebody show me how to do this?
I’m doing somethink like this:

add_action(‘admin_menu’, ‘mt_add_pages’);

function mt_add_pages() {
add_submenu_page(‘Posts’, ‘Key’,’Keyword’, ‘manage_options’, ‘menu1’, mt_add_pages );
}

values inside, is lil’bit random, i’m just want see does it works or not.
Thank you for attention)