Using classic Outlook for Windows in business environments
Windows Update --> Microsoft Update will update perpetual MSI versions of Office such as Office 2016.
For M365 Perpetual and Subscription, updates are automatic but can be initiated from Classic Outlook by clicking File, Office Account, Update Options, Update Now. I see from time to time that the Update button shows an update is available but if you check Update History you already have the latest build for the Office Channel, Update history for Microsoft 365 Apps (listed by date) - Office release notes | Microsoft Learn.
For New Outlook updates happen automatically but you can force an update if it's not updating for any reason. Right click the Windows Start button and click Run and put this command in the Run box and click OK: olk.exe --force-update