Each state has their own requirements. The best thing to do is contact your local office and ask them what documents you need and how to apply.
Contact your local child support office to apply for services. Your state may allow you to apply online. You might need to provide documents like birth certificates and information about your income and expenses like daycare and health care. Ask your local office for a complete list.
The United States has arrangements with other countries to provide child support services. Contact your local child support office to learn how your state handles international cases.