Use this guide if your Paddle dashboard shows a Vendor ID and Auth Codes rather than API keys. That means your account is on Paddle Classic.
Vendor ID, Auth Code and public key
Copy your Paddle Classic credentials into WordPress and test them.
Webhook alerts
Turn on the Paddle Classic alerts that subscriptions, refunds and disputes need.
Classic subscriptions
Classic subscriptions can be sold in USD, EUR or GBP. The plugin creates the Paddle subscription plans it needs the first time each product is bought.