ngyy123,
you have to go to the state of university (depend on where you go), then go into the license division, find out the profession you are in, then down load the form, and complete it, at the same time, you need to go back to your school where you get your license in hk, to mail your transcript over to the place for verification (also depend on your license and professional). If they accept your license, you may just need a computer exam. if Not, they will require you to re-take the subjects.
in order for you to take the license exam.
Like Nurses, depend on where they got their license, I got the EN in HK, and RN +BSN in Australia, so I just need a computer exam, and I got my license in 2 days (sure I did self studies for half year with 5000 questions and 72 subjects, before I go for the exam).