This has the best information of all in the Audacity to ACX videos!
ACX University: Setting Up Audacity: Part 4, Lesson 3
In Audacity, record in MONO, not stereo. Or save as Reduce to MONO.
Split screen for Audacity on left and book script on right, or for Audicity on lower screen and book script on upper screen.
Record narration. When you make a mistake, stop. Either record over it or start a new track to go back and fix it later. Use:
Shift Z = undo
Shift Y = redo
Shift X = cut
Shift C = copy
Shift V = paste
Shift K = copy all to end
Shift J = copy all to beginning
Export Track as [filename]_raw.wav with Encoding: 32-bit (float)
Drag and drop [filename]_raw.wav into Levalator. Keep this file in case you need it later.
Levalator will improve the file and make it much more even
[filename]_raw.output.wav will be saved wherever the [filename]_raw.wav is
Remove the old track from Audacity.
Drag and drop the new [filename]_raw.output.wav back into Audacity. You can delete this file later.
Select All (Ctrl A) and Effect >
Check Remove DC …
Check Normalize peak amplitude to Normalize to -3.0 dB
No check on stereo …
Export as [filename]_final.mp3 with Quality of 192 kdps
because an mp3 file is what ACX wants.
Keep this file, also.
Sound effects can be added, too.
Bit-rate Mode = Constant
Quality = 192 kdps
Channel Mode = check Force Export to MONO
Click OKAY on next screen (It is about music.)
Keep this file.
The [filename]_final.mp3 for narration or the [filename]_final_wSE.mp3 for narration with sound effects is the file to upload on ACX.