Fill in the recipient and your address; for bills, include an account number; sign it; keep proof of payment. 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. 1. Buy a money order for the desired amount. 2. Fill in the "Pay to the Order Of" line. 3. Sign the money order where it states – "Signature," "Purchaser," or "Drawer. " Do not sign the back of the document, that is for the recipient to sign.