The Petitioner (son/daughter) will have to file out form I-130 and pay the filing fee of $355
You will have to submit along with form I-130 a copy of the Petitioners Natralization Certificate, US Passport or Birth Certificate (showing that he/she is a US Citizen). You will also have to submit a copy of the Petitioner's Birth Certificate listing the Beneficiary as his/her mother.
Where to file
These forms witht he supporting documents should be filed with the Chicago Lock Box