There are many reporting requirements when you hire a new employee, including:
Lodging a tax file number declaration with the ATO
Set up a payroll function as part of your bookkeeping
Registering for PAYG with the ATO
Setting up a superannuation clearing house to pay their superannuation
You also need to make sure you have a signed employement contract which specifically states their working conditions, job description, rates of pay including all penalty rates, and any other entitlements such as annual and sick leave.
Ensure that you are aware of the minimum legal pay rates and allowances based on the relevant employee awards. This can often be a complicated area which you will require some professional advice on.