You can apply through the SSA website if you have a My Social Security account and meet certain requirements (e.g., a U.S. citizen aged 18 or older with a U.S. mailing address). Alternatively, complete the Application for a Social Security Card (Form SS-5) and submit it with required documents proving identity, citizenship or lawful status by mail or in person at your local office. For detailed instructions, visit the SSA's replacement card page.