A friend was surprised when I showed them how you can use the H4n to record directly into Final Cut Pro using the (Option + 0) -that's a zero- Voice Over tool.
1. Set up Final Cut so you're ready to record the VO.
2. Plug in the H4n using a USB cable.
3. THEN turn it on. (you can plug in the USB cable and select it after, but it's likely your H4n is off to begin with)
Note: the H4n may turn on automatically when you plug in the USB cable. There's an issue here that you may run into and should be aware of: if you hear a whine noise or some how unclean audio try plugging the H4n into it's AC power THEN turn it on, THEN plug in the USB cable and then go to Menu > Audio I/F > Connect. Don't forget to select your Frequency if you need to.
4. Select "Audio I/F"
4. Choose your kHz.
5. Select "Connect".
6. In FCP hit Option + 0 to open the VO Tool window.
7. Under "Source" select "H4".
8. In your TimeLine set an In and Out point for the VO
(NO you don't need to lay video slugs down to record VO…although that works as well, my friend's method, btw)
9. Hit record in the VO Tool window.
If you want to use your H4n to record directly into Audacity, say on a laptop that can't run FCP or something, you need to first go to Audacity's preferences and go to Devices > Recording > Device then select "H4" there then hit Ok.
You can also select the H4n as a playback device if needed, routing audio from the Mac to the H4n.