Tutorial
Step 1: Create a simple form as image below
Step 2: Edit Coupon Code Field > Content Tab > Field > choose Coupon Code type.
Next, click Add Item > fill Coupon Codes > choose Discount Type: Percentage or Flat Amount > Coupon Amount.
Step 3: Edit Total Field > Content Tab > Field > choose Calculated Fields type > add Coupon Code Field shortcode into the box.
Step 4: Your result
