You MUST be a U.S. citizen and you HAVE to register in order to vote. Click HERE to check the deadline for your state.
“Absentee and early voting: If you know you can’t make it to the polls on Election Day you can vote using an absentee ballot. While registered voters from every state can request an absentee ballot, some states require an excuse. Your state might also offer early voting. Contact your state election office or consult the National Conference of State Legislatures to learn more about your state’s voting options.” (Source: USA.gov)