To test out your connection for the data create a new page and save it to the site. With the page open go to the Databases tab of the application panel. In here you should be able to view the datasources that are available from the server. If not there will be a check list to gain access to the datasources asking you to enter your RDS password. Once you have established a connection to the datasources here you will be able to select them from within the tools.