You can use that migration tool to move your data from QuickBooks Online to QuickBooks Desktop. Before diving in, take note there are certain limitations and data that can't be exported from the online version. Additionally, it's not recommended to convert to QBDT if you're using the Multicurrency feature in QBO since your data won't be exported correctly.
When you're ready, start by logging into QBO and prepare your file for export:
Right-click the QuickBooks Desktop icon and select Run as administrator.
Go to File and select Close Company. Just leave QuickBooks Desktop open while you complete the rest of the steps.
Select Download tool to download and install the migration tool.
Once you've installed the programs, click Continue.
After that process, refer to the Step 4 - 6 section of this article to be guided in transferring your data and running the migration tool: Convert QBO to QBDT.