How to Hide Questions Deck Admin Menus

function plt_hide_questions_deck_menus() {
	//Hide the "Questions Deck" menu.
	remove_menu_page('qdeck-settings');
	//Hide the "Questions Deck → Questions Deck" menu.
	remove_submenu_page('qdeck-settings', 'qdeck-settings');
	//Hide the "Questions Deck → Questions & Levels" menu.
	remove_submenu_page('qdeck-settings', 'qdeck-questions');
}

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

Where do I put this code?