Like the other Articulate products, audio narration can be added in Engage. However, there is no provision for a music track. If you want to have music, you would need to edit the soundtrack outside of Engage and then import it as audio.
You'll need an interaction that you can work with. If you still have the one that you've been using for the other recipes in this chapter, you can use it. If not, create a new interaction of any type. I'll be explaining it with a process interaction, but the procedure is the same regardless of the interaction type.
You'll need to have a microphone attached to your computer to record with. A good-quality microphone makes a difference, as it will generally produce a clearer sound with less noise. You also need a quiet environment; if you can hear something, there's a good chance that it will be picked up by the microphone as well. Barking dogs, noisy air conditioners, and kids playing can all ruin a recording.