Where can I get the visa application form and be interviewed.

I am impressed with your explanations, however, there is no Hong Kong embassy in Nigeria. Do I need an invitation letter since I intend to go and purchase goods, please, what is the basic requirement to obtain a business type. I had visited Hong Kong over twenty times on business trips without any problems but that was over 18yrs ago when I changed business, my passport can prove this, but now the procedure I heard is so cumbersome.