Juniors interested in one of the US Academies (Air Force, Naval, Military(West Point), etc.) likely know a congressional nomination must be sought out by the student as part of the application process. This is something students should start to investigate as soon as is feasible..
The US Merchant Marine Academy posts some helpful information on their website that is applicable to any of the academies and may make this easier for you. When you get a chance, check it out:
Also, the US Coast Guard Academy does NOT require a nomination. Keep that in mind if you have trouble securing a nomination but are still eager to attend an academy.