I applied online. The process took 4 weeks. I interviewed at United Nations (New York, NY) in Oct 2017
Interview
They were very encouraging and efficient with the whole process (after you are scheduled for an interview, the waiting between application and notification is horribly long), and I was given a written test before going to the phone interview. They do not pay interns but I guess people want to get in since it's UN, an org that even your grandma knows!
Interview questions [2]
Question 1
A mini-case question where the goal is to maximize the resources needed in to transport civilians from war zones to safe areas.