Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I first of all have to ask whether the organ sounds would be MIDI sounds - if so, using the MIDI Out port and an appropriate cable and/or adapter would be appropriate - or 'regular' sounds - in which case a normal audio cable from the Yamaha's audio out jack to the input (sound card input) jack on the computer, would be right enough.
What you would be recording would be MIDI sounds if you were in MIDI Mode, otherwise it would be regular sounds.
After recording in Audacity, you would need to be logged in to iTunes, and do the import either by an automatic and pre-configured Sync (with the target being the directory with the Audacity recoding), or a specific Sync of the specific file or files.
But tell me a little more about the details you aren't clear on - I'm aware the above may cover ground that you already know - and I will advise you further. Thanks.