To use the postcode to MP match tool for state MPs in Western Australia you only need to change one line in the auto-generated code...
Your new code will automatically update the destination field to target each supporter's lower house state MP based on their WA postcode.
The "Zip" field is required in your action for this function to work.
This option only works if you choose the "No, send all emails to all targets" option on the "edit" step of your campaign (see screenshot below). The MP match plugin will ensure that emails are sent to the supporter's local MP (rather than all MPs).