Switch to "User Provided Storage" when using Azure Turbo Mode.
User Provided Storage allows you to provide your own Azure Storage instead of using one provided by Microsoft for the purpose of utilizing Azure Turbo Mode. It requires that you provide both your Azure Blob Storage Account Name as well as its corresponding Access Key by clicking the "Select" button to the right.
NOTE: User Provided storage will give you access to Azure logs for a longer period of time than Microsoft provided storage. It will also allow you to perform the migration faster with less throttling.
Steps to configure your Azure Account can be found here: