Use the discount manager tool in Shopify to create a "Discount Code" where customers will enter a code at checkout to receive a discount.
Here is an example code that we are creating that applies to a specific product and discounts a specific amount off the price.
To enable the discount code entry box on your cart page, select one of the three options in the app under Settings -> Discount Codes.
When the discount code setting is enabled you will see a Discount Code box on your cart page only when an offer that was configured in our App was met. If an offer was NOT met the customer will continue to enter the discount code at the checkout screen which will continue to allow the regular functionality of the discount code.
Enter the newly created discount code and click apply. Based on our setting of discounting from discounted price we should see a new total cart price.
Click apply and the additional $2 discount will be applied.
**Please note the limitations listed in the Discount Code Settings page of the application.