The NASS application is a preliminary application to USNA, so it covers grades, test scores (you can use PSAT scores in place of SAT, if necessary), activities, etc. There are a few opportunities for adding very brief explanations.
**For NASS applicants who haven't already put together a resume, it will make your life MUCH easier if you spend time between now and 1 Feb to put one together. List all sports, honors, awards, community service, or anything else important you've done during your HS years.**