Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 53)

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 53 (or-1))

For eng :
U need to put ur PC name (not User name) before ur db name same as on video sample