You should engage a Lawyer to prepare all relevant documents and file a petition in the prescribed format. Some of the documents which will be filed together with the petition are:-

(1) an affidavit verifying the contents of the petition,
(2) the child’s birth certificate,
(3) the marriage certificate of the adoptive parents if the petition is jointly made by the spouses,
(4) the consent of the natural parent(s) or guardian(s),
(5) the consent of the other spouse if one of them is the applicant.