You have to apply through HKICPA if you want to open any business with an accounting nature. Usually HKICPA will ask for a name, and the reason behind the name. Then, it will tell you to provide the CPA member associated with the business. In your case, 會計師事務所, there MUST be a CPA in the company. However, if you are opening a 會計事務所, then a CPA is not required.