Remind me how to use seekbar to control audio

I'm having to bring some old Presenter courses up to date with some narration, but can't remember how to enable the seekbar to control the audio playback.  

Have imported the files as MP3 and WAV, both of which play fine in terms of quality.  Sticking with MP3 for now due to file size.  Just need to figure out how to have the seekbar allow the learner to scrub back and forth.  At present, the seek bar only goes at its own pace (most slides are animated) but doesn't allow any learner interference.  Slides are not locked.  

Haven't played much with Presenter for over a year and I can't find anything in the forums/help pages either.

Any simple pointers appreciated.

Thanks