To edit a pay run, select the relevant pay run on the Run Payroll section.
Click on Edit.
This will allow you to go in and edit the pay run as needed.
If you have already submitted STP for this pay run, make sure you resubmit it after you have made the changes.
Please note that when you resubmit a pay run to the ATO, it will appear as an 'Update Event' in the ATO portal. The ATO reports will not show what you have changed the wages to.