You can go to
www.senate.gov and look up your Senators, and then
www.house.gov to look up your Representative. Pending on what state you are in, the MOC may already have the app open, or will open w/in the next two months. If they don't have the app open, write to either their in-state office or their office on Capitol Hill, and then play the waiting game.
Pretty much seconding what LFry94 said, haha
At least you gave a bit more helpful information than I did. I was about to leave to go swing dancing with my friends (don't make fun of me for being secure in my manhood.
) and didn't have time to type out a full, informative post.
To elaborate more on what I said earlier, visit one of the websites juliusc16 mentioned and figure out who your senators and representative are. Then go to each of their websites and try and find the section about applying for service academy nominations. There will usually be something you can print off and/or fill out online and then send in. (Usually requires a photo, affidavit of legal residence, a detailed list of your extracurriculars/awards/jobs/etc, a couple letters of recommendation, your transcript, ACT/SAT scores, and a ~400 word statement/essay about why you want to attend a service academy.)
You will have to complete this process for all three of your MOCs. (Members of Congress) Then, depending on where you live, you will either be required or invited to meet a board selected by each MOC to hold an interview that may/may not recommend you to your MOC for a nomination. Then your MOC will make the final decision and if you
do receive a nomination you will probably get a phone call anywhere from a week to a month or so later. (I found out "unofficially" the next day. Got the official call about five days later.) If you
do not receive a nomination you will probably get a letter in the mail a month or so later stating this.
Once you have a nomination, you won't have to worry about telling your academy of choice. They will be notified and your portal will update within a few weeks stating your nomination and who you got it from. Multiple nominations are great to have, so make sure you apply for all of them.
Hope this helps! Feel free to message me if you have any further questions.