From the portal you can type in the search bar "Azure2Git" and choose from Marketplace:
Click Create
Fill in the properties for deployment
Deployment will be done to your tenant.
Choose a region the same as your Azure DevOps/Azure resources are in.
You can change Managed Identity name
Choose the name for the application where you can configure your Azure2Git and see logs. For example, "tst-azure2git" will mean that the configuration site will be accessed on https://tst-azure2git.azurewebsites.net
Click on Review and create and review the settings and configuration
It takes a few minutes to deploy resources. When deployment is finished: