In rare cases -- say, programmers trying to create vintage video game sounds -- it may be desirable to record or export sound in the inferior 8-bit format. Audacity defaults at CD-quality 16- to 24-bit sampling, but it does allow you to manually change the sample rates to 8-bit.
Have the audio file you would like to convert into 8-bit already open within Audacity. If you would like all of your audio files to export in 8-bit, then no files need to be open.
Click the "Edit" menu at the top of the screen.
Scroll down to "Preferences." Navigate to "File Format" tab.
Click the drop-down under "uncompressed export format" and select the 8-bit option. You can export in an 8-bit format as a .wav file or as an Apple file. Click "OK."