Hi @One23412,
Congratulations on your second job!
You don't need to notify us of the second job. But you will need to provide your employer with a withholding declaration. On this form you at question 5 do you want to claim the tax-free threshold form this payer? You will select 'No'. This is your second job, so you won't claim the tax-free threshold. This is to make sure that you pay extra tax and don't end up with a tax debt when you lodge your tax return.