FarmChicDesign

Hi All, I have Chief X12 and I'm trying to use the auto stairwell function. I have created a staircase and from what I've read online so far, when I select the stairs, the "Auto Stairwell" button should appear but it's not. Can someone please tell me how to use this function in X12? Or if it's not available in X12, what is the easiest way to create a slanted ceiling above stairs to create a manual stairwell? TIA