I applied online. The process took 1 week. I interviewed at Challenger School (Sandy, UT) in Nov 2015
Interview
They begin with an opinion survey that covers lots of political questions like "what is the government's role in healthcare?", "what is the most important thing about the constitution?", etc. The end of the opinion survey asks for your personal views on Socialism. A skills assessment is next which is timed at 12 minutes long and seems like a typical IQ assessment tool.