Apply Hongkong visa for wife holding Vietnamese passport

I am an Australian-passport holder with Hongkong Permanent ID card and currently living in Vietnam with my Vietnamese wife. I am planning to take my wife for a 1-week visit for sightseeing and shopping. I understand that I can use my ID card to enter and exit Hongkong and my wife will require a visa. I am unable to obtain much infos on how to proceed with the application process other than applying through the Chinese embassy in Vietnam. Would appreciate any input/ advise give.