The YouTube Uploader should start automatically. If not, open it from your applications folder.
Official PDF and video operation guides for all modules are available at the Casio Support Manuals page. Support Software - Worldwide Education Website - CASIO casio video downloader
While there isn't a single official tool specifically called "Casio Video Downloader," Casio provides several official methods and software to download videos from their hardware (like digital cameras and keyboards) and to access their educational video content. The YouTube Uploader should start automatically