Overdubbing on Windows 8.1

I’m new to over dubbing with Audacity. Have a Windows computer using V8.1 OS. I have a file I imported and want to record my part and add it over the existing file. I have tried following directions in the help manual, but have not been able to make it work. What do you suggest?

Can you descripe more detailed, what you mean with “not working”?

Are you not able to create a second track below the first?
Or is this possible, but the track is empty?
Or is the recorded track full of audio and you do not know how to mixdown now both?