live view of sensor output on PC

Hello,

I want to make a vibration sensor application and I followed the example of: https://www.arduino.cc/en/Tutorial/Knock but I do not know how to monitor the sensor readings on my PC. How do I do this?

That link says "your board will send the string "Knock!" to the computer over the serial port. "

Do you want something else to happen? If so, what?

...R