The "Release Notes.txt" file in the download directory lists current limitations by version - the major one being that the service option is currently incomplete. I'm working on it!
That means you need to use the GUI for not only configuration, but ripping. At least for now. Once the service is functional you'll be able to rip manually through the GUI, or let the service rip new recordings automatically in the background.
You are correct, you merely need to point the ffmpeg folder setting to the subdirectory containing ffmpeg.exe. If the application can't locate ffmpeg.exe using the configured path, you'll get an error message in the output log window when you hit Start.
The non-supported URI message means that the application can't locate your Tablo. I'll work on a better message for that particular case. Did you get a list of Tablos in the top combobox? Try hitting the Refresh button? Nothing's going to work until the application sees your Tablo.
Worst case, enable Verbose logging and post the output. I'll take a look at it.
Thanks for your feedback!
PS - Please try today's version. I've added a bit of logic to select the first tablo in the list automatically if none has been selected previously.