This is the guide for Outlook Mac, Outlook365, and Mobile. If you are using Outlook for Windows Desktop, go here instead.
Step by step guide
The official release is due over the next few weeks. You can already install the add in manually by following the steps in this video:
(1) Manual Installation
Here's the URL to insert in the installation field for manual installation of the plugin (it's not an installation link):
(2) How to use the Add in