Bitcoins can be purchased on an exchange, or transferred via mobile apps or computers.
A third option: People compete to "mine" bitcoins using computers to solve a complex math puzzle -- the Bitcoin algorithm.
Industrial bitcoin mines devote their massive amounts of computing power to working on the algorithm, and are rewarded with an equivalent share of bitcoins. Currently, a winner is rewarded with 25 bitcoins roughly every 10 minutes.
Miners are lured to Hong Kong because of its proximity to chipmakers in China and the city's permissive regulatory environment.