Applied online and invited for an interview. They cover all costs. First you take a written exam about the topic of the project you applied for. Like exams in the university. they are not very challenging if you know the topic. The interview was about the position and skills required by the position. The panel consists of head of unit, project leader, officer that you will be reporting and generally one guy you will work with and an expert from a different unit. Questions depends on position but generally aims to understand the your knowledge on the topic and skills you have. Generally your attitude matters a lot. You should not be shy or over confident. You should convince them that you are the right person for the project. It helps a lot if you can demonstrate your abilities by giving references to the work you did before and listed in your CV.