To use Cloud Poodll you will need to have a Poodll subscription (free trial is ok) and your Cloud Poodll API secret. You can get your API secret from the API tab in your members area on https://poodll.com/member/?action=api . The first time you visit this page you will need to press the "Fetch new API secret" button. Your API username is your username on https://poodll.com.
If you have not registered your Moodle site URL you will need to, so that Cloud Poodll can authorize it. Register your URLs at the bottom of your member page: https://poodll.com/member . The registration key that is generated there is for Classic Poodll (the Poodll filter) and is not needed for Cloud Poodll.
There is no need to update your API key after registering new URLs, subscription renewals or upgrades.