Parameters in OLE DB

 Doing on a Report Server Project on an Access database.

How do I set up a parameter in this case
My query, in the Data pane,  is
SELECT * FROM qryR_ByLocation WHERE CatgID = @Catg

But when I switch to the Layout Pane, I get the error message
The data extension OLE DB does not support named parameters.
Use unnamed parameters instead.

Same message if I click Report/Report Parameters.

How do I use an unnamed parameter

Thanks
Vayse