The process for uploading audio files is the same as the process for uploading images.
You must be logged in to upload any file onto the website including the audio files.
Once logged in, click on the "upload file" in the sidebar.
Click on "Choose File" or "Browse" button and locate your file.
Finish the upload by clicking on the "Upload file" button. It's strongly suggested that you describe the file as well.
Mediawiki uses "Image:" prefix for sound files as well as image files. Thus uploaded sound files are also visible on the Special:Imagelist page. Placing sound files within entries is similar to placing images.
But when linking to sound files from an article use "Media:" as prefix.
For example if the file name was "SoundFile.mp3". To link to the sound file type:
[[Media:SoundFIle.mp3|Click Here to Play]]
Here is a test page for sound.