You want to poplulate your form with data from a database, or to populate the database from the form?
There isn't any way to import the data into the form in FormsCentral from a database. To populate and external database from the table on the View Responses tab there are no APIs to do it automatically but you can export to Excel or CSV and then import the Excel or CSV into your database: http://forums.adobe.com/docs/DOC-1383
With data from a database
Currently no method to import, but it is a highly requested feature, we do have a "Feature Request" form where you can vote on popular existing ideas or add a new one of your own: