Hi Menghan,
Please go to Modelling tab and click on ModelSettings. It will open up the configuration parameters windows. In this window, select the hardware that you want to use by going to hardware Implementation section.
Once you select the hardware and click on Apply, Hardware tab will be added to your simulink model toolstrip.
You can also open the following example model which is preconfigured for "Arduino Mega 2560" hardware.
arduino_gettingstarted
Hope this helps!
