To use "Lock and Key" promo codes, follow these steps: 1. Add the desired item into your shopping cart. 2. Verify that the item meets any requirements for the promo codes. 3. Proceed to checkout and find a field to enter your promo code. 4. Enter the promo code and confirm that it was entered correctly. 5. Complete the checkout process.
Please note that the exact process may vary depending on the website or platform you are using. Always ensure to read and follow the specific instructions provided by the retailer. If the promo code is not working, it may have expired or the items in your cart may not meet the requirements of the promo code. In such cases, try using a different promo code or contact the retailer's customer support for assistance.