When I applied the programme, I was studying for my master degree overseas. I submitted the application via email to the company's HR email address. After my application was accepted, I got an online assessment (just go google HSBC assessment and you will find out plenty of the samples.) After a few days, I got an email scheduling a phone interview with the HR representative. The HR interview was basic resume walkthrough and some simple behavioral questions. Keep in mind that HR representatives tend to ask follow up questions like "Can you give me another example?" or "Can you tell me how your peers react to what you did?" After a few days, I got an email inviting me to participate in an on-site assessment center.
It was a full day assessment including individual/group case study and presentations and role play. There was no skill based question but it did need some business senses to complete tasks (so don't be afraid if you are not business/finance major, but do get your self familiar with some basic business senses e.g. profit and loss analysis, etc.) There were very senior representatives from the bank to be the interviewers so be prepared to speak directly to multiple CEO one-downs.
If you can get the assessment center invitation then it means you are qualified for the job in many aspects. The only thing the company (and you) needs to find out is "fitness". The assessment center took a whole day for reasons and one of them was to allow the interviewers (HR assessors) to truly know you. You have to be yourself and see if the company fits you.