Petition for (Custody) (Visitation). These forms and instructions are available in the General Clerk's Office, Room 108, in the Nassau County.Complete General Form 17 to petition for custody or visitation. Bring a pen so that you can fill out the form. 2. After you give the form back to the clerk, you will wait for your name to be called. In this video we'll cover three terms to always include in the plan the steps to file for custody in New York and how to modify a custody agreement. A petition for custody would be filed in the juvenile, family, or domestic relations Court with jurisdiction over the child, at the county level. What to File (Custody):. • General Form 17: Petition – Custody, Visitation. You should file the custody petition in the Bronx.