Select a plane (increase segments to at least 40x40 for good deformation). Click "Convert to Cloth" in the PolyCloth panel. Start dragging with the "Grab" tool. You are now simulating.
Use the with a large radius to create major gravitational folds. For a curtain, drag from top to bottom. For clothing, start from the shoulders. PolyCloth ClothBrush 2.07 for 3ds Max 2016-2025...