Subtitles in Captivate

In Captivate your audio added to a slide will appear as a waveform in its own layer on the Timeline panel.  So you first need to select the slide and add the audio track to that slide before you will see it.  

You can add the audio to the slide a couple of different ways.  I usually just drag the WAV file either from my system or from the Captivate Library (if it's already there) and drop it onto the slide in the filmstrip on the left.  You can also add audio to the slide by first selecting the slide in the filmstrip then going to the Properties tab, then Options, then look for the Add Audio button.  

Captivate has other ways to adde audio to a slide by adding the audio to an object ON the slide instead of the slide itself.  This is called Object Audio.  But then you do not see the audio file on the Timeline view for the slide.  You have to open the audio for the object in a separate dialog.

You can also trigger audio to play when the slide begins by using the Play Audio action triggered by the On Slide Enter event.  However, that also will not show the audio on the Timeline panel.