Polar plots in HFSS

I am interested in plotting an electromagnetic scalar quantity along a circular path. It seems to me that creatinfg a circle, or maybe an arc so there is a defined starting point and setting up a polar plot ought to do it. However, whatever I try I the button to add a trace remains grayed out. Obviously I don't know what I'm doing. Any suggestions?

I don't know anything about the source of my newbie rating = 1. I have used HFSS for 7 years and I have over 40 years experience in rf cavity design.

Thanks - Jim