Where Do Files Go?

Graphics: Put category/product images wherever you like.

Previews: Previews can be uploaded through the Media Manager or by FTP.

By default the preview directory is images/mymuse/previews.
MyMuse adds to the Media Manager options so that you can upload mp3's through the media manager.
Previews will show up in dropdowns in the Add/Edit Tracks screens so it is best to upload them BEFORE creating tracks.

Downloads: The Main file for sale, also called the payload, can be uploaded through the Media Manager or by FTP.

By default the download directory is images/mymuse/downloads/mp3.
MyMuse adds to the Media Manager options so that you can upload mp3's through the media manager.

For security, if using apache web server, and your download files are within the web directory, confirm there is a file .htaccess at the top of the download directory

download_dir/.htaccess

The default is:
images/mymuse/downloads/mp3/.htaccess

This should stop direct downloads of files.
If it is not there, you can copy it from administrator/components/com_mymuse/assets/htaccess.txt -> images/mymuse/downloads/mp3/.htaccess