Becoming an intern was relatively easy. It required sending a letter to the head of the department, proposing to participate in one of the ongoing projects as an intern. This does require you to know which projects are ongoing, and if they suit you. After sending the letter and motivation I was accepted. In general it was a very quick and easy procedure to finish. There was no interview. The only thing required after that was to finalize some paperwork, and it is not possible to negotiate any remuneration.