Plugging your database is quite easy and shouldn't take more than a few minutes.
Connection to your database
To connect a database, you must give a name to this source, select the DB Engine type (PDO MySQL / MySQLi) and define the usual connection settings (host, port, user, password, schemaDB).
You source must be represented by its data model: it is a basic JSON configuration to describe the data structure (Types: objects and relations between these objects) and how data can be fetched (Connectors).
See the Data Models guide for more info.
You can either upload your own JSON model, or click on 'Build model form DB' to automatically generate the model.
It's just magic.