Create an output message file and an output message.
Basic method:
Create a new message file (extension .sfmxsd) to serve as the output message file of the flow.
Within the output message create a message element corresponding to each of the output parameters of the flow.
See the example in Step 1.2: Define the input, output, and variable messages for the top-level flow
Wizards:
See Steps 2 and 3.
Create an interface operation and store a reference to the output message into the interface operation.
You can store a reference to the output message into the interface at the same time that you store a reference to the input message (see Step 2 in the instructions in The input message of a flow).
If you have not stored a reference to the output file into the interface operation yet, you can do so now:
Open the operations file that you created earlier (extension .wsdl).
Expand the operation the you want to update.
Add a reference to the output message of the flow to the interface operation (see Working with the operations editor).
See the example in Step 1.3: Create the interface operation for the top-level flow
Specify the operation from Step 2 as the interface operation for a flow.
See Step 3 in The input message of a flow.
At the end of the flow store the output parameters of the flow into the output message:
Open the flow in the flow editor.
See the example in Step 4.5: Set the output parameters of the flow CatalogOrder).