This must be done via the Audible app which can be added to student Chromebooks. Please do not use the Audible website :)
If you are looking for Everlost that audiobook is in the German marketplace. Alll other titles are in the US marketplace. Below are instruction on how to change your marketplace country.
Audible Audiobook - an audiobook which can be played on a school kindle or using the audible app on a school Chromebook
Folletshelf Audiobook - an audiobook that can be accessed through Destiny Discover and can be played on any laptop, computer, phone, tablet, etc
Sora - Sora is a new platform for accessing ebooks and audiobooks, can be played on any laptop, computer, phone, tablet etc either in an internet browser or using the free Sora app