I registered to vote for mayor last year, does that mean I'm registered for this election and I can just show up at the polls and vote for president? Do I have to register every year to vote? Sorry, I'm nineteen and confused. :(
I think once you are registered, you are in going forward, but voting for mayor has nothing to do with a federal election, they would be separate registration.
You can register on the day of the vote at the polling station though.
At least that is how it is in Canada.
You should have gotten a voter registration card, that and an ID is probably all you need to show up at the polls on election day. I don't know what programs are available in your state, but I recommend signing up for a mail in ballot that way you won't have to worry about these things in the future.