Answer
If you would like to enter Reportable Fringe Benefits for an employee, you can do this in Employees >> Tax Rates >> Reportable Fringe Benefits.
To add in benefits for a particular financial year, click the pencil icon on the right hand side for the relevant financial year.
In this next screen, you can also set Fringe Benefit Tax exemptions for the employee for the selected financial year.
If you add or change reportable fringe benefits after you have already finalised that financial year through Single Touch Payroll, run the end-of-year finalisation again for the affected year so the ATO receives the updated amounts. See How Do I Process End of Year Using Single Touch Payroll?