I) Online application: CV mandatory. Must answer two brief questions about your interest in joining BB and your skills for the position.
Advisable to include cover letter and reference letter (if applicable).
II) Phone interview: a 30-min "speed-dating" style interview that will bombard you with questions in order to see how you can handle the pressure while at the same time showing your interest in joining BB and specifically the area & position as well as responding to some competitive market questions (why BB and not TH-RTRS, or FactSet...).
Good advice: be succint and do not diverge from the topic of the question. Keep the calm in order to answer with clarity.