To access the Function Definition settings, click on the name of the function.
You can optionally give your function a name using the "Function Name" field. If you choose not to, a default name will be provided for you.
Add any inputs and outputs your function needs. You must provide a name for each input and output, and can also set their types (ie, text, number, etc).
You can now use your function via the Function Call module.
Outputs are returned from the function using the Return module.