I applied online. The process took 1 week. After the online application, they sent me personality and preference test on my email, which I passed. Then I was invited to a phone interview via email. You need to select date and time convenient for you via HSBC interview booking system. During phone interview you need to give an example of situations: When you notice something went wrong, when you helped someone etc. The interviewer was not nice nor helpful. I didn't pass the phone interview. Next step is Assessment Centre. If you fail you can apply again after 1 year. Summary:
Step1 online application
Step2 personality and preference test
Step3 phone interview
Step4 assessment centre
Good luck!