When I filed a petition for my relative I was a legal permanent resident (green card holder). I recently became a U.S. citizen. How can I upgrade the petition?

Make a copy of your Naturalization Certificate. Send the copy - NOT the original - to the National Visa Center, 32 Rochester Avenue, Portsmouth NH 03801-2909, with a letter containing the beneficiary name and case number of the petition you want to upgrade. The National Visa Center will send the beneficiary any additional forms and information that may be required.