We've got two ways to localize a support video. The main way is to localize the captions file and email it to Michael - pretty simple. The other way is to record a localized audio track which Michael will add to a new version of the video, recorded with a localized version of Firefox (we'll only do this with select videos in select locales because it's time consuming).
Currently, we're working on localizing these videos for Firefox 29:
You'll see that each video has a corresponding caption file. Please localize the text while leaving the time information alone. When you are finished, email the text files to Michael (mverdi at mozilla dot com). Michael will then add these to the video where they will be available to viewers.
Because this is time consuming we'll only do this for select videos in select locales. Don't record an audio track unless Michael or Joni contacts you about doing this.
To record the track you'll need an audio recording program and, idealy, a microphone.
Once you've got Audacity and a microphone, translate the appropriate caption file to use as your script. The caption files (and videos) can be found here. You can use the video as a guide to what will be happening. You don't have to say everything as fast as the English version (may not even be possible in some languages). The video can be lengethened or shorted as required to fit the audio.
When you are done:
Michael will then record a localized version of the video and add in your audio track. He'll upload it to YouTube and send you the link so that you can put it in the localized version of the article.