To Choose Data source we have used three type of icons to segregate the type of data on boarded
This icon is used for transactional data
This icon is used for Metric data
This is used for other types of Datablocks
To select a Datasource, hover over the Datablock header and click the 
icon.
...
If you have an existing report that contains the measures desired, you may use the "Select Report" drop down menu select an existing report from your list.
Some Datablocks, such as the Drillthrough Datablock, require that you click the 
icon to access the Datasource.
