Help adding audio after video play

Hi. I am new to articulate and I am having some trouble with a particular feature. I have added .mp4 video in one of my slides. It is full audio/visual (it's a commercial) and my ID would like for me to add additional audio to be placed once the video has played. So, end scene, then the audio narration comes in. I cannot figure out how to do this. I'm in 2009. Any suggestions?

Thanks in advance! 

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