Recruitment is final phase of the selection procedure and it is NOT handled by EPSO (they only deal with 'selection' of potential new officials but they don't themselves recruit). It is up to the specific Directorate General or EU institution to decide who they wish to invite for a final interview from among those who had been placed on a reserve list.
Recruitment happens after 2-3 candidates are invited for a 'classic' interview in which they are asked questions on their knowledge in the specific field, motivation and personal profile. A medical examination is required and if all goes well, a job offer is extended towards the candidate who then becomes an EU official, with a 9-month probation period.
See also:
Diploma Requirements, Pre-Selection Tests, Assessment Centre, Reserve List
Related link:
New To EPSO Competitions and Recruitment Exams?, EU Agency Selection and Recruitment Database