If you want to incorporate a Hong Kong company, you should firstly to submit the form and the certified printed copy of Memorandum and Articles of the Company together with the registration fee to Company Registry. You can download the statutory forms form the web site and find the details of the prescribed fee there. After 7 working days, you can receive a letter from Company Registry for collection of the Certificate of Incorporation.
You can visit the web site of Inland Revenue Department, you can find more detials about the taxation on businesses. Here is the link
www.ird.gov.hk
You should also apply for the Business Registration Certificate within 1 month from the date of commencement of business. You should collect the original application form from the IRD office.
About the taxation, in USA is worldwide.