The following article describes how to install the report Phishing addon for Office 365.
When a Phishing Campaign is underway and users start receiving phishing emails, they have several choices: they can either open, inspect, and ignore the email, click a link, provide their credentials, and fall for the phishing attempt, or report the suspicious email.
Report Phishing Extension is a special button that appears on the email message taskbar in the right top corner. This allows users to easily report suspicious emails and helps organizations assess the effectiveness of their anti-phishing training. It also provides valuable feedback on areas where additional training may be needed.
In order to proceed with getting the extension, please navigate to the phishing menu in your admin console, and press on the "Extensions" menu: 
Insert the email address to which the reported emails will be forwarded into the "Report To Email" field & press save afterward:
We recommend creating a direct email (or group), for that. Example: incident-response-team@yourdomain.com, reportedemail@yourdomain.com, etc.
Once the email is saved, you can use the manual according to the platform you are on.
Installing the extension:
As an Admin, navigate to the Microsoft AppSource page and look for the extension via the top search bar.
Once on the page, press Get it Now.
You will be forwarded to Microsoft 365 Admin Center, Integrated Apps section. (requires admin login)
Once there you will be presented with an option to deploy the app, select the desired user(s)/groups to whom the app should be deployed, and press next.
Next, accept the app permissions and proceed further:
Once done, proceed to finish deployment:
Once the app is deployed, you should see the Wizer extension icon when you open up emails
The extension will show up as a tiny Wizer logo in the web version of Outlook as in the screenshot above, yet if you don't see it due to the number of extensions used, you can pin it.
To do so, navigate to Outlook settings > View all Outlook settings
In the settings, select Email > Customize actions and make sure the Report Phishing extension from the Wizer checkbox is selected.
Once the above steps are done, you should be all set.