Hi, the only way i know is to listen to the original recording through headphones, whilst playing second track. Mind you, i am refering to recording vocals.
It’s a setting in Audacity and it’s slightly different depending on your computer, but I would totally use headphones anyway.
Before I dig for it, please be clear that single computer management of multi-track sound is always going to have “Latency.” Even if you do manage to record multiple tracks one after the other, they will probably not overlay perfectly without sliding one or the other sooner or later on the timeline. You can minimize that effect by recording all the parts against one sync track instead of using that last track to record the current one.
Audacity Preferences > Audio I/O > Those Little Boxes At The bottom. Pick the ones that give you the least damage. The delay and damage will never hit zero. Also, if you’re on a Windows machine, the Windows Sound Control Panel will get into the act, too.