You have to pass a competition. 

Hi, Please kindly note that your query has been forwarded to our expert, please see below his response:

For contract staff function groups II, III, and IV within an institution, the maximum duration is limited to 6 years. But EPSO, OIB, OIL, the representations of the EC and EP, the delegations and the agencies can offer 3acontract for an indefinite period of time.  Cumulation of contracts is possible ex: 6 years with the EC and another 6 with the Council. Temporary staff contracts article 2a to F applies different maximum delays.Of course, the permanent jobs accessible through a successful completion of a competition are by far the most attractive ones offering numerous career opportunities.I trust the above has brought clarity to your question."

If you require further assistance, whether about eligibility (qualifications and professional experience) or the language regime, or you are planning to apply for an EPSO or an internal competition of an EU institution, we provide tailored and personal guidance, therefore I recommend scheduling a session with our great expert, Mr. Gillis, who will be happy to support you in the most effective way possible. You can book a session using the following link:https://eutraining.eu/products/personal-coaching?meta=products_coaching-session_application-assistance-oaching_172202#application-assistance-oaching-with-luc-gillis