Usually, two approaches of building ORM models are used. Model-First approach means that database development starts from scratch with the model designing. So, you have to describe all of your model entities, properties, etc., and after that generate the database for your model (connection parameters for data source will be set up).
Database First approach is applied usually when you have a legacy database. It means that database objects are converted to model entities with the help of reverse engineering.
Entity Developer supports both approaches and it also offers a mixed approach. You can use Update to Database and Update from Database wizards to synchronize your model and database in any direction. For example, you can generate model from the database, then edit it, and apply these changes to the database with Update to Database Wizard.
This section provides information about given approaches: