To display a clickable link below your card invitation (while collecting Rsvps through Paperless Post):
1. On the Enter Details page, click "Additional options".
2. Click the toggle next to "Include additional information for your guests", and add your link there.
3. Click the "Save" button.
To direct guests to another site to Rsvp (without collecting Rsvps through Paperless Post):
1. On the Customize page, use the arrow to the right of the card image to bring up the Reply Card.
2. In the menu on the left, click "Reply Card Option" (http://bit.ly/1Jk3GnL).
3. Choose "Card with website link" and click "Done Designing".
4. On the Enter Details page, enter the URL, and the text to appear on the button.
You can preview how each of these options work to see which one is right for you.
How to format a URL correctly