If you don't have a Paddle account already, sign up for Paddle and finish the required account setup. Paddle will verify your business information which may take a few days.
When your Paddle account is ready, go to Payment Methods in the Reflow admin panel and click Add Payment Method -> Connect Paddle. A dialog will appear, requesting the Seller ID and API key of your paddle account. We require this key in order to authorize requests to the Paddle API, which will allow us to create subscriptions and handle payments on your behalf.
You can find your Seller ID and API keys in Paddle > Developer Tools > Authentication.
If you want to work on your Paddle integration in test mode first, you can create a Sandbox Paddle account and enter its Seller ID and API Key in the sandbox field. In live mode all subscriptions will be connected to your regular Paddle account, while in test mode your sandbox account will be used instead.
Click the Connect button to finish the setup.
Before you can use your Paddle account for payments, you will need to configure the Domain and Default Payment Link settings. These steps are required by Paddle for authenticating that all checkouts are hosted on a domain that you own.
You can learn more about why they are necessary and how to configure them in the Paddle docs: