To use "St Frock AU" promo codes, follow these steps: 1. Search for the St Frock AU promo codes you wish to use. 2. Copy the code. 3. Finalize your purchase on the St Frock AU site, select either Checkout or View cart to initiate the payment process. 4. Paste the copied code in the designated area. 5. Click the Apply button to incorporate the savings into your total. Remember, some codes may apply only to full-priced items, or they may be applicable only when you spend over a certain amount. Always check the terms and conditions of the promo codes to ensure they can be applied to your purchase.