The final STP screen is used to confirm the final yearly totals that are sent to the ATO for each employee. This should be completed on or before 14 July each year.
You are able to submit the proposed values, or overwrite them if you wish to make a change.
Once the final STP file is sent, your employees' income statements are in their mygov account are updated to 'Tax Ready'. They can then do their individual tax returns.
Further instructions can be found here.