If you have a SQL server database that contains georeferenced data, you can add that data to a Feature Layer in the GIS Editor. When you add a new layer, select the Microsoft SQL Server option. That will bring up a window for you to connect to your SQL database.
Enter the SQL server's name. Then configure how you want to log on to the server by either using your Windows authentication or using SQL authentication. Once the credentials are set, click connect. Upon successful log in, the server fields will become available to you to select from.
Now that you are connected to your SQL server, select a database that you wish to use. Then select the table name that you are bringing into the GIS Editor, and finally, select the column that contains the Feature ID and click OK. This will open the Style Wizard to add the table to a new feature layer.