If you are lucky enough to have a Poodll coupon code, you can use that on the Poodll payment page. Applying it will give you a full or partial discount on the package/plugin price. 

To begin, visit the product page for the product you are interested in and follow the links from the pricing table to the checkout.

If you are not logged in, you will be asked for information such as your name and email address. If you already have an account you should login first and return to the checkout page. 

On the payment page you can choose from "Invoice(offline)" or credit card as payment options. On this page  look for the "Have a coupon?" link. Tap that and enter your coupon code.

If you are upgrading from a free trial, then you can use the same API user and secret that you currently use. If this is a new account be sure to pick up your API user and API secret also from the member's page. You will need to enter those in your plugin's settings page on Moodle.

Good luck