i would like to listen to one channel while recording on second channel
That’s overdubbing. Provide a base or rhythm track, play that back into headphones while you record the guitar part on a second track. And then play any combination of those back and sing for a third track. And so on.
http://manual.audacityteam.org/man/tutorial_recording_multi_track_overdubs.html
There are ways to mess this up:
— The settings for recording internet sound don’t work with overdubbing.
— You can never hear yourself while you’re recording unless you have a microphone or other device with zero latency monitoring. You can’t just plug headphones into the computer.
— The computer has to be powerful enough to play your backing tracks and record the new track at the same time.
Koz