Download an FTP transferring program such as Fetch (Mac) or FileZilla (PC). Follow the installation instructions and launch the program.
Enter the host name (FTP address) when prompted. Enter the password, if any, when prompted.
Select the music files you wish upload to the server. The most universal file format for music is MP3, so sticking to an MP3-encoded music file when uploading to a widely used server is the safest bet.
Drag and drop the music files into the program. They should begin uploading to the server.