Write your address in the purchaser section. Include your account number if you're paying a bill.Decide on the money order amount. It's similar to signing a check. You'll see a line for the purchaser's signature, usually on the front of the money order near the bottom. This page includes forms, fees, and instructions for all domestic business entities, foreign and domestic Registered Agents, and Washington Trademarks. To fill out the money order, you will need to "Pay to" U.S. Department of Homeland Security.