Syncing sound and animation on the timeline

Hi there, I'm new in Articulate storyline but I was tasked to come up with an online safety training for office personnel. When I was browsing the tutorials few months back, I encountered one tutorial which I cannot find right now.  It's all about putting "marks" on the timeline (seconds bar) as to when I intend an object should appear based on the narration.  It's like manually editing the timeline to synch with the narration but a lot easier as it uses a marker.

Please let me know where can I find that tutorial.