In the main report you will need to create parameters that match the type in the subreports.
Then link these to the subreports...
1. right mouse click on each subreport, select change sub report links
2. select the newly created parameters on the left and move to the right
3. on the right side select the first parameter
4. below the left list, there is a comboBox subreport parameter field to use, from this list select the corresponding parameter, repeat for all parameters and subreports
Hope this solves your issue?