High pitch feedback when config for Audacity

Windows 10+ Audacity 2.2.2
I’m trying to use Audacity to record my online English software with students round the world for review/marking of their work. Presently I have a seperate tablet, but this is difficult in a noisy enviroment when I have to migrate to a cafe when my hotel system is down.
I’ve read some internet notes and config’d my W10 laptop (Dell Inspiron 13 7000 2-in-10) to use stereo mix from the task bar, but when I enable it, the feed back howl starts.
The Audacity is set to use Windows wasabi and loopback on Recording Device.
What am I doing wrong? I’m trying to get it to work with speaker/mike input, but eventually to go to a AH-327 headset when in a noisy cafe.

Any ideas anyone? I am not a tech geek, knowing only basics. Thx

With your configuration you have created a “feedback loop”. The output is feeding back into the input, so the sound rapidly goes round and round, getting louder each time, quickly resulting in “howl!”.

Using a microphone and speakers is one likely source of the feedback (sound from the speakers leaking back into the microphone). When using a microphone it is essential that the speakers are turned off (use headphones).

Also, ensure that “Software Playthrough” is off (“Transport menu > Transport Options”).