To become a U.S. citizen, one must be a permanent resident for at least 5 years, be at least 18 years old, be of good moral character, demonstrate proficiency in English and knowledge of U.S. civics, and not have any disqualifying criminal convictions; then gather documents like a green card and criminal records, fill out the N400 application online, review it with staff in Seattle; next have an interview to explain the application, and if approved, attend a ceremony to take the Oath of Allegiance and become a U.S. citizen.