using mic successfully

Windows

I seem to recall I could play in a track to Audacity and then I could put the earphones on so the second person could hear to sing but one couldn’t hear the first track in the air, only on the phones. I don’t remember how to do this will you point me in the right direction in the manual please?

Tick playthrough “Other tracks while recording (overdub)” …
https://manual.audacityteam.org/man/recording_preferences.html