How to give a free product to customer that refers a friend?
In order to give a customer a free product when he refers a friend, you need to configure a coupon amount to be equal to that product price, and also add product id so that it can be applied only on that product. Check the image below to see example configuration:
So under plugin settings -> Coupon Settings tab, chose coupon type to be Product Discount. Coupon Amount should be equal to the product price, the product that you want to give for free. And lastly, under products, you need to add that product id. You can get product ID by hovering the product name under Products screen, like shown on the image below:
That it. Now, go to Email tab, and under "Email message", write up some text so that customer knows that code he received will give him the free product.