Although Camtasia is an amazing program, Screencast-o-matic is a heck of a lot easier to use. These instructions will describe how to use Screencast-o-matic to add voice over to a Prezi, since it's not possible to add audio right to Prezi. I'm happy to say that these instructions work the same on every platform and browser! (as far as I know right now anyway!)
1. Put the finishing touches on your Prezi. It should be 100% done.
2. Download the Prezi. The yellow arrows on the image below are pointing at the Download option. When the box comes up, choose the top option - "Export to Portable Prezi to present offline." It will first make it into a downloadable format, and then ask you to click a link to actually download it.
Why are we downloading the Prezi? Because we want to be able to size it correctly to look good in it's final form. The only options to view Prezis are in the very wide format (like above) or full screen. If you record it right off of the Prezi website, you will get black bars on the top and bottom. It is not possible to record it full screen because you can't get the screencast-o-matic window to come up if you have Prezi full screen. Even if it did work, you wouldn't have enough control over the size, which could vary considerably depending on your monitor size and screen resolution. Trust me, you want to download it. This is also a good option if you are presenting somewhere and don't trust that there will be an internet connection.
3. A zip file should have downloaded. You need to extract the files for them to work. Right click on the file (wherever it downloaded - probably into your Downloads folder) and choose Extract All.
5. Plug in your microphone if it is not already plugged in.
6. Go to the screencast-o-matic website. Click "Start Recording" on the top right. It will do some Java stuff and will ask you to allow it, then should bring up a recording window.
6a. Note: Screencast-o-matic runs on Java which is a tricky program that apparently needs to be updated constantly. It can be a hassle to get screencast-o-matic working the first time. If you are having problems, try a different browser - for instance, if you're using
7. Make sure it is using your mic. Click the drop down by the mic area and find yours (it will say something like Logitech USB device if you have a Logitech brand device that plugs into your USB). Make sure that the green things are moving, which indicates the mic is picking up audio.
9. Make your Prezi window fit the recording area. Do not change the recording area. You can drag the bottom right of the Prezi window to change its size.
10. Click Record (the red button). If you make a major mistake, just start over. If you make a minor mistake, keep going and then when you are done watch the whole thing and see if that minor mistake bothers you. I usually anticipate a few trial runs (aka mess ups) and get a good one after a few tries. The free version of screencast-o-matic does not allow editing. If you want to edit, we need to move up to Camtasia.
11. After recording, upload to YouTube HD. It should be nice and clear.
Here is a video showing how to do this. [Updated 10/22/2012]