Currently JuicyAds API only supports Popunder data at this time.
To obtain an API Key, click on the "My Account" link in your right side menu, then "Settings". then click the "API Keys" tab, then click "Generate a NEW API key" button. A link to the API documentation is also available.
Here is a link to the JuicyAds API documentation: https://api.juicyads.com/docs/v1.txt