If you meet certain requirements, you may become a US citizen either at birth or after birth. Use this form to apply for US citizenship.Be at least 18 years old at the time of filing Form N-400, Application for Naturalization. This form is available to file online. Our family immigration law attorney is committed to keeping families together. The IRC can help you to petition to bring your family members to the US, apply for citizenship, green cards, work authorization, travel documents, and more. You'll have to fill out form N-400, the Application for Naturalization within the U.S. Citizenship and Immigration Services (USCIS). Form I-130: Petition for Alien Relative is the first form you must file to start the marriage-based green card application process. Processes all naturalization applications and provides the Court with a list of the candidates selected to be naturalized in the Federal Court. If you or a loved one wishes to apply for adjustment of status, our green card attorney in Salt Lake City, Mark Naugle, in can help you with the application.