Try it with headphones on. I don't hear the taps when I use my computer's speakers but do with headphones.

2 ways to do it. You can either use the space bar or tap your screen (like on an iPad or iPhone) in the gray area field of play. Not sure if you are referring to Rhythmic Parrot or Rhythmania. In Rhythmic Parrot, you are listening to the rhythm play and playing it back with the click track. In Rhythmania you are tapping the presented notation back after the count-in.

There's still a 3rd way: clicking your mouse inside the same area @Ken Wilkens described but...by the time you reach level 80 your finger might be falling to pieces!