mssql: update readme

public/app/plugins/datasource/mssql/README.md

-# Grafana MS SQL Data Datasource -  Native Plugin
+# Grafana Microsoft SQL Server Data Source -  Native Plugin
 
 
-This is a data source for connecting to MS SQL servers.
-You can use it to connect to any mssql server and get grafs/tables.
+Grafana ships with a built-in Microsoft SQL Server (MSSQL) data source plugin that allows you to query and visualize data from any Microsoft SQL Server 2005 or newer.
 
 
-check the docs from more info.
+## Adding the data source
 
 
+1. Open the side menu by clicking the Grafana icon in the top header.
+2. In the side menu under the `Configuration` link you should find a link named `Data Sources`.
+3. Click the `+ Add data source` button in the top header.
+4. Select *Microsoft SQL Server* from the *Type* dropdown.
+
+For more information, check the [docs](http://docs.grafana.org/).
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