It helps if it's something you WANT to do. Don't do it because you think it makes your application look better.
USNA is concerned with your academic standing, your standardized test scores, your physical fitness and overall health and wellness, your Varsity sports participation, extracurricular stuff, etc.
Put forth your best application. Get great grades. Take the PSAT, the SAT and the ACT. Get great scores in Math and English.
Take AP classes and take the AP tests for all of them.
Stay healthy and make healthy lifestyle choices. If you're not in great physical condition, get there.
Go to USNA.edu and read every page and every drop-down menu and link. Everything is there.
Good luck.