Workplace giving is detailed in the ATO page: https://www.ato.gov.au/Individuals/Working/Working-as-an-employee/Workplace-giving-programs/.
The key aspect of entering Workplace giving deductions is to use the nominated "Workplace Giving Withheld" liability account.
There's several ways to enter a workplace giving:
1. Entering payroll using the Pay Wages feature
From the Transactions tool bar > Employees > Pay Wages
Configure the payroll accounts as displayed:
An example of the transaction coding is displayed below:
2. Entering a direct payment
This shows and example of a journal for a Workplace giving deduction
DR $1000 Wages
CR $300 PAYG
CR $50 Liability Account: Workplace Giving Withheld
CR $650 Cash at Bank