x10 don't offer the back up wizard which is a standard feature in cPanel, to try and keep the server load as low as possible I believe.
Anyway, to back up your website you'll need to download all files/folders to start with. This can be done via FTP or cPanel's File Manager. I would recommend to ZIP the content first, then download it to reduce the overall size (compression) and make the download quicker.
If you've got any databases, simply go to phpMyAdmin, then select your database on the left and select Export. From there, it's fairly straight forward.