Adding subreports to report templates
To add a subreport to a report template
The report appears in the Report Designer.
In the Toolbox, click the Subreport tool.
Position the cross-hair pointer on the template where you want to insert the subreport, and then click and drag the mouse to define the subreport's size.
When you release the mouse button, the Subreports dialog box appears. For field definitions, press F1.
Type the name of the subreport in the Subreport name field.
From the Select the field that will link list, select the field that links the main report to the subreport, and then click OK. Depending on the type of report being created, this is usually the contact, group, company, or opportunity name.