If I recall correctly, I got an email within a couple days that contained the specifics regarding the where and when and what I'd need for the interview.

The interview itself is a panel interview with tell me about a time style questions, one or two technical questions and some get to know you questions. There is no sim, but there is a scenario based portion in front of a paper tiger. You'll be given a scenario to begin with, and will act as the Captain and you have a short time (I think it's 7 minutes) with which to work. You don't have to solve the problem, but make sure you're using CRM and keeping the operation safe at all times.

In between each portion you'll wait in a break room with the other applicants. During this time there will be Frontier people with you, usually pilots, whom you will have the opportunity to talk to and ask questions of so make use of your time! Also, prior to each portion you're escorted by a Frontier employee, usually a pilot, who will ask basic questions, go over your resume, etc. Overall it can be a long day if you have a larger interview group but it is a good opportunity to let them get to know you and for you to do the same.

I'd highly recommend an interview prep service. Centerline, Emerald Coast, etc. There are gouges out there that serve as a good reference but the questions and the scenarios change so don't use them as your sole source of preparation. Congrats on the interview and good luck!