In a DAW

Contour is an audio effect, not an instrument. Insert it on a track and it listens to whatever that track is receiving. All three plugin formats come from the same installer and run the same engine, so pick whichever one your host prefers.

Ableton Live

Create or select an audio track, set its input to the interface channel carrying your microphone, and insert Contour from the audio effects browser. Arm the track to hear Contour's output; you do not need to record to use it live.

Delay compensation

Contour tells the host how much delay it adds: about 24 ms of tracking, plus whatever buffer you are running. Hosts with plugin delay compensation use that figure to keep the track lined up with the rest of the session on its own. If a track sounds early or late against the others, check that delay compensation is switched on in your DAW's audio preferences. A few hosts ship with it off.

Next: troubleshooting.