I have Canada passport and plan to go to HongKong and then to China. What is the procedure?

You don't need a visa to enter HK if staying there for less than 90 days.

To visit mainland China, you need to get the visa in advance. First, fill in the application form here: cova.mfa.gov.cn; you need to choose the right place you are going to lodge the application. Then, make an appointment to submit the form and other requirements. It usually takes 4 working days to get the visa after the successful submission.