How to Hide Media Library Assistant Admin Menus

function plt_hide_media_library_assistant_menus() {
	//Hide "Settings → Media Library Assistant".
	remove_submenu_page('options-general.php', 'mla-settings-menu-general');

	//Hide "Media → Att. Category".
	remove_submenu_page('upload.php', 'edit-tags.php?taxonomy=attachment_category&post_type=attachment');
	//Hide "Media → Att. Tag".
	remove_submenu_page('upload.php', 'edit-tags.php?taxonomy=attachment_tag&post_type=attachment');
	//Hide "Media → Assistant".
	remove_submenu_page('upload.php', 'mla-menu');
}

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

Where do I put this code?