A Chromebook can join via 2 methods:
1. DisplayNote App on Chromebook (recommended)
Chromebooks with access to the Google Play store can download and install the DisplayNote Android application by searching for 'DisplayNote' in the Play Store.
For instructions on how to access the Play Store (and a list of compatible Chromebooks) please see Google's support pages - https://support.google.com/googleplay/answer/7021273?hl=en-GB.
2. DisplayNote for Chrome browser (http://join.displaynote.com)
For those devices that do not yet have access to the Play Store, they can use DisplayNote in their Chrome browser. Note DisplayNote for Chrome browser has some limitations - please see this article.
Note: http://join.displaynote.com is not supported with DisplayNote NEC Edition - please use the DisplayNote NEC Edition app from Google Play.