newbie - visual analyser is a sound card oscilloscope - the hardware is the soundcard, the software displays the microphone input on your screen.
For example, this is me humming, with microphone pickup, and frequency meter selected
Probably don't want to exceed a volt or so for input.
I'll see if I can pick up a stereo jack tomorrow and provide some better guidance.
I would start with creating a square wave output from arduino into a potentiometer with the center tap and ground into the PC, slowly dial it up until the scope peaks out, then measure that and make up a scope probe with equivalent voltage divider for looking at 5v signals.