To create a Payment gateway for Adyen configuration, you'll need to configure the API Key, Merchant Account, and Adyen Live URL
API Key:
you can generate API Keys in the Adyen Dashboard. Go to Developers> API Credentials and then select the Create New Credential button.
Each location will have its own API Key
The modal Create API credential will appear. To create it,
Select the Web service user option
The Username will be autogenerated and can't be changed
Enter the Description (e.g. Adyen Configuration)
and then select the Create Credential button
The page will refresh and you'll be navigated to the new API credential details page from which you can grab the API Key.
Copy the API Key in the Adyen dashboard, paste it in the API Key in the Gateway Configuration in the Admin Dashboard, and select the Save button.