Adding sound to animation

I want to add sound to a 3-1/2 minute animation I have almost completed. I want to be able to project the animation (I don't know if that changes anything).

2 questions:

1)Is it best to add the sound in Animate? What I research seems to suggest that, but 6 years ago when I made an animation in Flash, I exported it before adding sound. Can't remember much about it. 

2)My animation file has 33 folders, each with several layers. Is it best to make a separate folder for sound or add sound layers to each pertinent visual folder? I plan to add a lot of separate sound effects. I imagine organization would be easier if I add each sound layer to the pertinent folder.

thank you