How to Hide Secure Downloads Admin Menus

function plt_hide_secure_downloads_menus() {
	//Hide "Secure Downloads".
	remove_menu_page('opsd');
	//Hide "Secure Downloads → Secure Links".
	remove_submenu_page('opsd', 'opsd');
	//Hide "Secure Downloads → Files".
	remove_submenu_page('opsd', 'opsd-files');
	//Hide "Secure Downloads → Settings".
	remove_submenu_page('opsd', 'opsd-settings');
}

add_action('admin_menu', 'plt_hide_secure_downloads_menus', 12);

Where do I put this code?