CFA and HKSI paper 1,7,8/9

CFA is more important, as CFA is now the most famous qualification in the field of finance.
Passing the HKSI paper 1,7,8/9 is only the requirement of stock brokers, so only you want to apply such posts, do those paper. But if you want to apply financial analysts, propably you should study CFA.
About registration, you should register online, here is their website:
http://www.cfainstitute.org/
By the way, they only accept the final year student to apply, so if you are year 2 student, you can just study the syllabus first. The website has some study material for online purchase, also, you can buy some other study package outside the web.
I'm not quite sure about study material about hksi coz no intention to study it, sor!
Hope it helpful!