First step: You will need to apply for the job. There are many channels available but using a headhunter or finding a friend already working here to endorse you is the best way. Besides that, you can also play the online Quintiq puzzle challenge to secure at least a phone interview.
Next, the phone interview. IMHO it's only there to assess your verbal English skills.
If you passed that, you will be called to take a written objective exam. Back when I took it it consisted of 20 questions split evenly between maths, logic and programming. This test is considered tough since even now I see only 1 out 5 candidates make the passing mark (55 this year, was 60 last year). After the test, HR will call the candidates one by one and if you pass, there will be a one hour session with HR where you will disscuss hiring, prior work experience, compensation and whatnot. Feel free to ask any question you can think of since the HR are very accomodating and eager to convince folks to join (especially with the low pass rate in the written exam). They have KPIs too you know ;)
Now, if everything went well you will get a call within 2 days to set up a 2nd interview with one of the directors. They will send you a case study and you will usually get one or two weeks to prepare. All I can remember is it took nearly 3 hours, and that there were many difficult puzzles/scenarios to solve.