Installing the Sophos Plugin to Outlook

This document is kind of a mystery.  The installation points to a generic Microsoft document.

https://docs.sophos.com/central/customer/help/en-us/ManageYourProducts/PhishThreat/SystemSettings/PTOutlookAddin/InstallOutlookAddinPhishThreat/index.html#deploy-add-in

I've got a manifest file that I've downloaded.

The linked article from Microsoft in Step 3 does not describe what I'm supposed to do with this.

What I found is after I've downloaded it, I log into Microsoft 365, go to Settings > Integrated Apps.  On the Deployed Apps tab, I have to select Upload custom apps, then navigate to the XML file to add it and select the users I would apply it to.  

Perhaps the documentation could be clarified so others can do this as well?