If you are already in court for another kind of case like divorce, custody, or paternity and you then realize you need to move with your child, ask the judge if you can change your complaint. Use a "Motion to Amend." File an “Amended Complaint” with your motion. It should be the same as your first complaint but also asks the court to allow you to move with your child. See the directions for adding this request to the end of the complaint in If You Are Getting Ready to File a Case.
When you file your motion, the court will give you a hearing date. The hearing is not about whether you can move with your child, but about if you can change your complaint to ask to move. At the hearing, the judge will probably let you change your complaint.
Just because the judge allows you to change your complaint does not mean they give you permission to leave the state with your child. The judge will decide if your child can move when they have a hearing or a final trial on your complaint.