DeForce Problem

I've started the DeForce tutorial that involves draping a blanket across a woman lying on a bed: https://www.daz3d.com/forums/discussion/comment/2982696/#AddonDForceModifier. Here is where I got stuck: Select the plane in the Scene Tab, then from the main menu select Edit/Object/Geometry/Add dForce Modifier: Dynamic Surface.  I couldn't find the 'add dforce modifier' after Geometry. I uploaded a screen shot so you can see what I mean -- the 'add dforce modifier' option isn't there at all! What am I missing here? I am absolutely stumped and I haven't even learned anything yet!