Applied on company's website. There is an IQ test pretty much that is required and takes around 45-50 minutes to complete. Have a pencil and paper ready. I heard back within a week and was e-mailed asking for my college transcript and to schedule a phone screen. The phone interview lasted 30 minutes and was full of generic behavioral questions, and they asked about things on my resume.
I was contacted after the interview asking for an on-site interview in Dover, NH. It was with a Director and an Assistant Director at the same time. They asked questions about my resume and wanted specific examples of projects I had worked on, etc. This interview was less of the BS behavioral questions and more of "do you sound like you know what you're doing?" I threw around as many big words as I could think of and I was offered the internship about two weeks after that.
Once you get an offer, they do a pretty intense background check. Make sure you talk to all your former employers and warn them (if necessary) because the WILL call them if you list them.