How do I buy ETFs in HK?

I'm curious to know, how exactly does one go about purchasing ETFs, or Exchange Traded Funds, in Hong Kong? I've heard that they offer a convenient and cost-effective way to invest in a diversified portfolio of assets, but I'm not quite sure where to start. Could you please walk me through the process step-by-step? What are the key things I should be aware of, and are there any specific requirements or restrictions I should be mindful of? I'd really appreciate any guidance you can provide.