The way to make it work is to open the main report in design mode and right-click on the subreport. Select the option to edit the report links. When this dialog box pops up, you have to link the group field in the main report (this is done at the top part of the dialog box) with the group field in the subreport (this is done at the bottom part of the dialog box).
By linking the two reports based on this common field, the data in the subreport will be filtered so that you it only shows the details for that current group.
Since you are new to Crsytal Reports, you might want to check out my Encyclopedia book. I have a chapter on subreports that walks you through the steps of how to create/link them as well as tips and tricks for advanced usage. You can find out more about my books at
Amazon.com or reading the
Crystal Reports eBooks online.