We have just organised our international driving license. I think you have upto 12 months to use an existing recognised license from another country, but after that you should obtain a HK one. Firstly you need to complete the appropriate form on the above link posted by Vegemite_Kid. Then follow the instructions on the form as to what you need to provide. I needed to take down originals and copies of our HK ID, Overseas Driving Licence, Passport, evidence of residence in HK (a bill of some sort), and the completed form. Depending on the type of license you currently hold, you may need to take additional information. I completed mine and my husbands. It was around $900HK for a 10 year licence and you can pay via EPS or Cheque. I went to the office and the whole process took about 10 minutes (which has handy as I had my young daughter with me). You have to go back around a week later to collect the actual document, and it is used in conjunction with your HK ID. All in all I found it a very easy process, even when I had to process my husbands for him.