Tutorial
Step 1: Create a simple form as the image below:

Step 2: Edit Coupon Code Field > Content Tab > Field > choose Coupon Code type.
Next, click Add Item > fill Coupon Codes > select Discount Type: Percentage or Flat Amount > Coupon Amount.


Step 3: Edit Total Field > Content Tab > Field > choose Calculated Fields in Type > add Coupon Code Field shortcode into the box.


Step 4: Your result.
