Azure AD and App Registrations
Azure Service accounts can be chosen from an Existing Account or created automatically on configuration. This gives greater control and provides the API access required by the VBAzure appliance. Organizations will likely prefer to set this themselves, and not let the application create. In order to use a preexisting account, an App Registration must be made in Azure Active Directory. Help Center Link
That is all. Easy setup, just need to know where to go. Use the information you gathered to configured the Azure Account in the Veeam Appliance. Then get rid of that Notepad file. Rememebr- the Secret will not be available again- you will need to recreate it should you need to reconfigured. Not a big deal- in fact it allows you to revoke and setup new Secrets for different apps.