There are several processes involved in becoming a US citizen. Most common is when one has been a Legal Permanent Resident and lived continuously in the US as a LPR for 5 years or LPR has been married to a US citizen for three years and has been a LPR for the same three years they may qualify and may be able to apply to become a US Citizen, depending on each individuals history. Other processes to become citizens are deriving citizenship from a parent or acquiring citizenship automatically.
This is a long process and an important step which must be carefully researched in order to determine eligibility. The client must also be prepared in order to be successful at the Citizenship interview and test required by the USCIS. ODIS offers Citizenship classes in order to provide this preparation. See Classes.