Audacity wont record winn amp

I am running win 7 and I have a blue yeti usb mic.
when I record on audacity it records my voice fine, but it will not record anything off the comp including my winn amp. When I turn on winn amp with usb mic plugged in, not a sound, but as soon as I unplug the mic the sound begins.

Audacity will only record from one sound device at a time. If you have all analog equipment, you can tell Audacity to record from Stereo-Mix and get all the sounds on the sound card, but USB microphones don’t use the sound card.

Koz

How do I tell audacity to record from stereo mix?

I’m not a Windows elf, but there is a write-up.

http://manual.audacityteam.org/o/man/tutorial_recording_audio_playing_on_the_computer.html

A couple of blocks down, you get to split up to the various operating systems.

Koz

See also:
http://wiki.audacityteam.org/wiki/Mixer_Toolbar_Issues#cp
and
https://forum.audacityteam.org/t/how-to-mute-usb-mic/30767/2