When using Final Cut Pro (or Final Cut Studio), the Turbo.264 HD can be accessed directly through the application's Export command to create H.264 formatted files.
To use this feature, make sure you have installed and launched the Turbo.264 HD software at least once (and after any Turbo software updates). This is required to install the Turbo.264 HD components for QuickTime, and will overwrite the components used for any previous versions used with a Turbo.264 device.
Once the software is running, plug in the Turbo.264 HD to make sure the software recognizes and initializes the hardware. After this you can quit the Turbo.264 HD software.
Then from within Final Cut Pro, when you want to export using the Turbo.264 HD hardware, select Export > Using QuickTime Conversion... from the File menu. This is slightly different than it was with the original Turbo.264.
Selecting this brings up the Save window. From the Format menu choose Elgato Turbo.264 HD and from the Use menu, select from the built-in presets or choose Edit... to create a custom set of file attributes.
To find out more about Turbo.264 HD presets and custom settings, please refer to these additional articles: