Once you have filed the application, the USCIS will send out a letter informing you about when and where you can get your fingerprinting for Citizenship & Naturalization done. On the given date, take the appointment letter and some form of identification with you.
USCIS requires applicants and petitioners for certain immigration benefits to be fingerprinted for the purpose of conducting FBI criminal background checks. To better ensure both the quality and integrity of the process, USCIS processes fingerprint cards for immigration benefits only if an authorized fingerprint site prepares them. Authorized fingerprint sites include USCIS offices, Application Support Centers (ASCs), and U.S. consular offices and military installations abroad. In general, USCIS schedules people to be fingerprinted at an authorized fingerprint site after an application or petition is filed. USCIS charges $70 per person (for most applicants) at the time of filing for this fingerprinting service. Please check the instructions on your Immigration application or petition form to find out if you must be fingerprinted.
To make fingerprinting more convenient for customers, USCIS has opened 84 freestanding fingerprint sites (ASCs) and 46 sites located in existing USCIS offices. USCIS now employs a system where fingerprints are taken and submitted electronically to the FBI. By using electronic fingerprint technology, USCIS has significantly reduced processing times for criminal background checks.