I met a Fidelity recruiter at a networking event and gave them my resume. I also had a friend that worked at Fidelity which is always a plus. The interview is intense and challenging, especially if you are not familiar with common interview questions. The phone interview asked behavioral questions and know about the products/services that Fidelity provides.
The in-person interview day started with an introduction PPT presentation. You are with the other candidates for the first hour. Everyone was really eager to stand out, so do your best to pipe up and ask some questions, even if it is about general information. Know common terms such as stocks, preferred stock, stock symbol, etc. We then took a tour around the building and met a couple of employees.
Then two hiring managers took candidate by candidate into a separate conference room for an 1 hour + interview. The day you go in for your interview, know the current unemployment rate, what is going on with the Federal Reserve, the current stock indexes quotes such as the Dow Jones and S&P 500. Know exactly why you want to work at Fidelity and not another investment company - very important.
Overall, have great answers to common interview behavioral questions and you'll do great.