Tascam FW-1082 Sound Card Problem

[delatone]

This is probably going to sound trivial to a lot of people, but i just got fw-1082tascam and want to how i can record a sound with the "what u hear" option. It's no longer available in my 'sounds and audio devices' option anymore. is this even possible with this mixer? Another way of describing what I'm trying to say would be if, as a simple example, I played an mp3 song on my computer and I wanted my audio recording program to pick up the signal (i.e. acid or sonar), how would I get it to do that now? i've been driving myself nuts trying to figure it out and finally decided the smartest thing to do would be to ask someone on this site. any answers/feedback would be much appreciated. thanks.