How to go from "master sound" to "line in"?

Hey community, I have one problem.
I just want to play music from controller to maybe TeamSpeak 3 you know what I mean, but I'm not getting sound.
One of my friend told me I have to go from master to line in, but Idk how, I was googling for hour with no results... If anyone would help me it would be great.
I just want to play music from controller to maybe TeamSpeak 3 you know what I mean, but I'm not getting sound.
One of my friend told me I have to go from master to line in, but Idk how, I was googling for hour with no results... If anyone would help me it would be great.