Go to the competition page on the aha website. They are supposed to post links for the individual judging locations I believe. If not, the comp page should have the instructions when they open later.
You're going to need to set up a login, even for the people who've done this before.
Edit: Had to wait until I got back to my desk to post this link...too hard to do on a smartphone
http://www.homebrewersassociation.org/pages/community/news/show?title=national-homebrew-competition-registration-opens-tuesday-feb-26


