We provide you with several ways to do that:

- Browser-based uploader
You can select multiple files to upload to your
account using just your browser without the
need of installing any software

- Desktop - Uploader for Mac & Windows
You can download our free applications for
Mac OS X and Windows in order to upload
your library. We recommend you to use this one
when you're planning to upload more than just
a few tracks.

You can find both products at http://www.tunesBag.com/ (Library > Upload)