You can deploy the outlook addin to your Microsoft 365 users automatically.
You must proceed from the Microsoft 365 Admin Center, in the Settings->Integrated Apps section (https://admin.microsoft.com/Adminportal/Home#/Settings/IntegratedApps) and select "Get Apps"
Search for "PhishBrain" and click on "Get it now"
Follow the wizard selecting desired deploy options, you can deploy it only for yourself, entire organization of specific users / groups.