You can connect to an existing database using the Server Explorer window of the Visual Database Tools. Once you do so, the databases hierarchy will show as nodes and files in Server Explorer. Depending on the database management system of the database you are connected to, you may be able to edit the data and data structure.
In Visual Studio 2013, you can connect to a SQL Server database from either SQL Server Object Explorer or the Data Connections node in Server Explorer. SQL Server Object Explorer provides a view that is like SQL Server Management Studio. To open this explorer from the menu bar, choose View, SQL Server Object Explorer. For more information, see Connected Database Development.