The Data Stores Tools, located just above the Data Stores List, enable you to configure the Data Stores List to display all the available data layers or only the layers that overlap your current Main Map View.  

Displaying all the data available on the DAP server
When clicked, this tool will display all the data available on the DAP server.

Displaying only the data available in the current map view
When clicked, this tool will display only the data available in your current Main Map View.

Finding Help
When clicked, this tool will open the associated help topic.

To select the data to compose your map, go to the Layer Manager