vents

Hey everyone, been lurking on this forum and using it as a resource as I work on my first gbody that I recently bought, decided to join to request some help. I'm not new to working on vehicles, but I haven't owned a carbed vehicle before, nor have I owned anything older than 1989. My Cutlass is...

Can someone please point me in the right direction. I get air through my defrost but can’t change it. Iv done some reading but can’t pin point what’s actually worked. Which pieces in the picture below need to be replaced to get air to the dash vents???