Mona4,
First, there is no "ground only references" You can show the hidden terminals of the HFSS design in circuit, since an n-port is really a 2*n-port, with the references hidden. To show the references, right-click on the HFSS symbol in teh schematic, and choose "Edit Symbol-> Pin locations..." The dialog below will come up and choose "Add individual reference pin per port" in the reference pulldown.
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