Once downloaded, run the patch file to update Sonicfire Pro to version 5.7.5.
When it has completed, launch Elements and invoke the SmartSound option. It should launch Sonicfire Pro and automatically obtain a serial number if you do not have one. You can then select from one of your owned titles, enter the custom parameters for the track, and click on the Send button to send the audio file to your Elements project.
UPDATE: Sonicfire Pro 5.7.5 is only compatible on Mac OS 10.5 though 10.8. It is not compatible on the Mavericks OS 10.9. To use Sonicfire Pro on Mavericks, you will need to install the latest version of Sonicfire Pro 5.8. Unfortuantely Sonicfire Pro 5.8 is not compatible with the Elements 10 & 11 integration, so you will need to use it as a standalone application. Elements 12 does not contain a SmartSound plugin for Sonicfire Pro.