I want to add field object to an existing repeating frame.But when I drag the field, new frame is generated.
See Image below.
I want to do is put the field F_PO_NUMBER under R_INVOICE frame.
I'd suggest you to
P.S. As you already have the R_1 frame (which is useless), I'd suggest you to remove (in paper layout editor) it, as well as current F_PO_NUMBER field (visible on your screenshot).