MicroFour.StrataFrame.Data.ConnectionManager.AddRequiredDataSourceItem("", "SQL Connection", Data.DataSourceTypeOptions.SqlServer, "StrataFrame", "This connection is used by all design-time components and houses the business object mappings, meta-data, messaging, and localization data.")

The string in red above is the name of the key that you will need to specify.  It determines which connection you want to use when you reference the DataSources collection.