To download and install the QuickBooks Connection Diagnostic Tool follow these steps:

1. Open your web browser and go to the official Intuit website.
2. Search for "QuickBooks Connection Diagnostic Tool" in the search bar.
3. Locate the official download page for the tool.
4. Click on the download link to start the download process.
5. Save the downloaded file to a location on your computer.
6. Once the download is complete, navigate to the location where the file is saved.
7. Double-click on the downloaded file to start the installation.
8. Follow the on-screen instructions to complete the installation process.
9. Once the installation is finished, you can launch the QuickBooks Connection Diagnostic Tool and use it to diagnose and resolve connection issues with QuickBooks.