Hi junjieshao,
Express Generator is an add-on to EA Studio and as such it is necessary to purchase EA Studio before purchasing Express Generator. Having said that, I recommend first learning how to use EA Studio before learning how to use Express Generator. I have put together a process to follow to start learning how to use EA Studio at no cost. Click on the following link to start your learning journey:
https://eatradingacademy.com/forums/topic/ea_studio-how-to/
Alan,