You can learn how to Export domain database using Guest Post selection tool as follows.

Open the My Projects page in the header.

Click the Create Project button or click on the current project's name to open it.

You will be redirected to the page of your project.

Click on the arrow button in the right corner and select the data export format that suits you:

After that you will see the following window:

Once the file is ready and downloaded, it will appear in the Downloads folder on your computer.