You set the drill-through definition up in the package, so that the Promotion Plan Revenue report is available to any report based on the source package, and you use dynamic drill through, instead of defining parameters.
You must have the IBM Cognos Business Intelligence samples from the deployment zip file IBM_Cognos_DrillThroughSamples installed to follow this exercise. By default, the samples are installed in the Public Folders in IBM Cognos Connection.