Use the carddecks URL scheme to launch the app and, if used correctly, add a new deck of cards to the app.

Application homepage:
iTunes link:
HTML Link example: <a href="carddecks:///add?YES%2FNO,000000,00ff00&YES&%20NO%20,000000,ff0000">Add a Yes / No deck</a>
Native application URL string example: carddecks:///add?Faces,00ff00,000000&%e2%98%ba&%e2%98%b9,ff0000
Extended example:
Tags: decks cards

Check out the 0xc0 website for more info.