Need addition information on Test Object Input

We have a mobile application with a list that contain a Dynamic Radiogroup of checkboxes items. The user can select multiple items from the displayed items. The checkbox must be identified by the associated text. We thought we could use the Test Object Input screen to pass in a variable called ID, Index or Instance. We have tried all three but the object cannot be found.

Is there additional documentation on using the variables for the Test Object Input screen? Perhaps I am missing something on setting the Param Type or the Param and value.

Thank you,