You just email the admissions rep for your area and let them know. They’ll put it in the kid’s file

My DS’s varsity team generally announce captain shortly after the season starts. But it is winter sports, which means it starts around mid November. my DS is very likely to be captain next year which is his senior year. Will it be too late to put in common app for ED or EA? I know this won’t change profile much, but still would like to have it. Any one has similar experience?