Maestro includes an update notification feature that is enabled simply by connecting your Mac to the Internet. Maestro will ping Apogee servers to determine the latest versions of Symphony I/O firmware and software, and notify you if updates are available. If updates are available, the dialog shown below appears.

Click on the link provided in the dialog and download the Symphony I/O firmware and/or software updates.
To update firmware:
Connect the Symphony I/O USB port to your Mac using a standard USB 2.0 cable
Unzip the Firmware Updater package
Launch the Firmware Updater application by double-clicking on the Firmware Updater icon
Click “OK” to update firmware
To update software:
Unzip the Software Installer
Launch the Software Installer by double-clicking on the icon
Follow on-screen directions
Re-start after the installation is complete