Your Hong Kong Identity Card (HKID card) will be the most important document you need to acquire once you land in Hong Kong. You need this to open a bank account, rent a flat, hire a helper, apply for a credit card and start utilities accounts (gas, water, phone, Internet, cable TV, etc).
Generally the process of obtaining a HKID is very efficient, especially if you book online which can be done at:
https://www.gov.hk/en/residents/immigration/idcard/hkic/bookregidcard.htm
The address of the Immigration office in Wan Chai is:
8/F Immigration Tower
7 Gloucester Road
Wan Chai
MTR – Wan Chai Station, Exit A5
Opening Hours
9:00am - 4:30pm (Mon - Fri)
9:00am - 12:30pm (Sat)
Closed on Sundays and public holidays
Organise to do this as soon as you can after you arrive in Hong Kong.