Have you got the software to create highly compressed audio files in MP3 format from recordings via your microphone? If not, download opensource software Audacity
and make sure you also download
and install the MP3 encoding file. Instructions on how to make sure your MP3 encoding works are here
You can then upload these files in your assignments or discussions. Just make sure your files are not bigger than 2 MBs. You will need to use the settings suggested in the tutorial in the link above.