Once the KillPhish Lite Google Workspace (G Suite)/Gmail add-on has been installed, your users can report an email by opening the message and clicking on the icon to the right. Next, they simply need to click the Report Email & Sender button. The email will then go to the Reporter Email Address and Additional Reporter Addresses. The user will need to be a target in the phishing portal to report emails with this plugin.
Note: KillPhish for Gmail, due to technical restrictions from Google, does not have the ability to score emails, collect email headers, display custom helpful tips and reported success message, or delete emails from the user's inbox after reporting.