How to Hide WP Mailster Free Admin Menus

function plt_hide_wp_mailster_menus() {
	//Hide "WP Mailster".
	remove_menu_page('wpmst_mailster_intro');
	//Hide "WP Mailster → WP Mailster".
	remove_submenu_page('wpmst_mailster_intro', 'wpmst_mailster_intro');
	//Hide "WP Mailster → Mailing Lists".
	remove_submenu_page('wpmst_mailster_intro', 'mst_mailing_lists');
	//Hide "WP Mailster → Queued Emails".
	remove_submenu_page('wpmst_mailster_intro', 'mst_queued');
	//Hide "WP Mailster → Servers".
	remove_submenu_page('wpmst_mailster_intro', 'mst_servers');
	//Hide "WP Mailster → Users".
	remove_submenu_page('wpmst_mailster_intro', 'mst_users');
	//Hide "WP Mailster → Groups".
	remove_submenu_page('wpmst_mailster_intro', 'mst_groups');
	//Hide "WP Mailster → Archived Emails".
	remove_submenu_page('wpmst_mailster_intro', 'mst_archived');
	//Hide "WP Mailster → Settings".
	remove_submenu_page('wpmst_mailster_intro', 'wpmst_settings');
}

add_action('admin_menu', 'plt_hide_wp_mailster_menus', 11);

Where do I put this code?