The way you set up a payment plan with respect to owed back child support is for you and the mother of your child to enter into a written agreement setting forth the amount of arears owed and how much you will pay per month to pay it down over a period of so many months.The stipulation will be filed with the court where there is the child support order in place against you. There will then be an order signed by the court memorializing the stipulation. I suggest that you consult with a family law attorney to assist you in the matter that you have written about.