To apply a discount code to Quick Sale, click the item you want to sell and then click Go To POS.
You'll be brought to the Add-Ons screen. If you'd like to add additional products to the cart, you can do so here, but otherwise, you can see that the item you selected to sell as a quick sale is already in their cart. This is indicated by the "1" next to their name.
Next, select Check Out and confirm the items in the cart.
Enter the discount code and click Apply.
