To use a Vintage Foundry Co promo code, follow these steps: 1. Find the Vintage Foundry Co discount code that you want to apply. 2. Copy the code to your clipboard. 3. Choose your items on the Vintage Foundry Co website. 4. Start the checkout process and enter the offer code at the Vintage Foundry Co checkout. 5. All done! The discount should now be applied to your order.