For the OP, you have received an excellent spread of advice on the process of applying and many other aspects of the SA journey.
My two cents is - take some time to think about the minimum 5 year commitment to active duty afterwards.
During my time as on the USNA Commandant's staff, I saw dozens of mids voluntarily leave USNA because they got caught up in the competitive thrill of the "hunt," and didn't focus on whether a military career, short or long, was a good fit for them. Too many said things like, "my school counselors were so excited I got in, I hated to disappoint them, " or, "my family was so happy they wouldn't have to pay for my college education, I couldn't tell them I didn't want to go after all," or "Grandpa Joe was in the Navy, and once he found out I was applying, I felt I couldn't let him down," or, "my aunt and grandfather were grads, and I never felt I had a choice from the first time they took me to an A-N game," or even, "I got the nom and the appointment, and everyone was just so crazy excited, I felt stuck." I realize it's hard to know as a junior/senior in high school exactly what you want to do, but the more you can find out about life AFTER the Academy (or ROTC or any commissioning program), the better a decision you will make about attending one. A SA is a 4-year launching pad to something you can't walk away from easily after you start your junior year there. The system is designed to shed plebes and cadets quite naturally along the way, for all kinds of reasons, voluntary and involuntary. Some of the saddest were those who realized that neither a SA nor a military commitment was right for them, and kicked themselves for not having the maturity to step back from the process back in high school and really, really think about what this meant for the next 9-10 years.
If you get clear on your motivation for the short and the long term, everything else falls in place. Good luck!