You can file a petition for child custody in your county's Superior Court. If you are divorcing, the petition will be included in your divorce papers.This article discusses registering other states' custody and support orders in Texas so that Texas courts can change and enforce them. This guide includes forms and instructions for a letter and affidavit to request that the court register an out-of-state custody order in Texas. • To file your forms online, go to E-File Texas and follow the instructions. How will a judge make decisions about child custody? Where can I file for child custody? You will need to file a Petition for Modification of Child Custody and attach the Affidavit to the Petition. Your county may also require some additional forms. Your child must have lived in the Georgia county for at least 6 months prior to the filing.