When creating dialogues, you have the option to record audio or select one. I already have recorded sound files, just unsure where to put them so that they appear in the selection list. I am a creation kit and TES modding noob so the more details, the merrier. Thanks in advance.

It's painful, but here is what I do:

1. Create the new response with just the text, click the OK button (twice, once for the spellcheck, once to close the window).
2. Double-click your just created response to open that same window again. Except, in the "Voice Filename" area, there should now be the name (and below, the path) to the sound file the game expects.
3. Rename your existing .wav file to to match what the game has auto-generated (you can copy the expected file name from that gray "Voice Failename" area and paste it when you right-click your file and choose "rename") and put it in the specified location--you may need to manually create the proper directory the first time.
4. Double-click OK again to close, then re-open the response window again.
5. This time, highlight the sound file in the list, choose the "From WAV" radio button at the bottom, after which the "Generate Lip File" button should become available. Click it, wait a second, and you're done--on to the next response!