My son, who is marine option, just got done going through the whole sideload application process. As a sophomore, however because he switched over from AFROTC. They wanted him to have at least one semester of observation and grades from his classes. A marine option freshman was going through this at the same time. They started the application process when directed by the captain, which was after they came back from the Christmas holiday. He told them exactly what to do, what forms to fill out, how to take a picture, and how to do a tattoo policy form. He then collected all the information and mailed it to the appropriate place.
It is quite a bit different than doing it all on your own you went through initially. The captain writes recommendations and has input into ranking. I believe the Navy option can apply for a three-year scholarship during their freshman year, but I do not believe that is available to the marine options.