In most situations, you can file for custody in the "home state" of the child. You need to file in the county and state or the child resides primarily.1. File for custody. You may file in the family court or a court of a different name that hears custody cases. You can either fill the forms out yourself or allow your attorney to complete them for you. Step 2: Fill out your paperwork. Complete e-fillable forms on your computer or obtain physical forms from your county court or online. How to fill out the form of Custody Complaint;. Listed below are the forms that are required to be completed as well as the petitions that can be filed. How do I file a petition for child custody in Tennessee?