Using a PAT is how you authenticate as a user, so that you can configure your Service Principal (SP) - if you follow this link, there's a guide to the next steps (you're on step 3 now)

Thie article explains a bit more on how to setup up the SP in Azure DevOps: Use a Microsoft Entra service principal for automation with Azure Databricks Git folders - Azure Dat...

Hope this helps 🙂