How to blend edges in HFSS? (Urgent)

Hi everybody!

I just want to know how can I select and edge of a waveguide filter in hfss and blend it with a radius. I know how to do it in cst, but now I need to compare with hfss.

Thank you all.

what does that mean?
what does blending the edge with the radius mean?

Can you do it by subtracting a circle cylinder from a squared one?

i think you can just select an edge and add a fillet