To calibrate you joystick within Windows go to the Control panel, then to Game Controllers (XP/Vista) or Gaming Options (2000) and select the model of your joystick, push the properties button within the Game Controllers/Gaming Options window. Select the Settings tab, press the Calibrate button, and go through the Windows calibration following the directions on screen.
If your joystick is not registering afterwards within the properties window it may not be connected correctly or there may be a problem with your computer.
Note that FS One does not use the Windows joystick calibration information. Instead you must calibrate the FS One USB Interface and controller from within the simulator, and the simulator will then use that calibration and ignore the any Windows calibration whether you performed that calibration or not.