How do you add custom sounds into a map?

I am generally new to Valve Hammer Editor and I've been looking quite a bit thanks to all these amazing tutorials and such out there. I've learned how to make a scene with choreographed scene or what not and the campaign I'm creating requires some custom narrating.

I've done a little research and it seems that you go about this by adding the sound files into a BSP? I just downloaded Pakrat and Gfscape, can anybody explains how I add audio scenes/sounds to my map, I would greatly appreciate it.

I took a look at the colours bsp in Pakrat and it seems they added their own sounds there, how did they do that? Thank you.

If this question was answered in a previous thread, I apologize for not finding it in the search, please just post the link below.

Again, thanks.