Just off the top of my head, if the item already has a smoothing modifier put on it, then you’ll find it under paramaters—> general—> mesh smoothing.
If it doesn’t have a modifier already on it, then select it in the scene tab and then (i think go to edit—>figure—>smoothing modifier. That may not be right. (or edit—>object—>smoothing modifier if you’re working with an object, not a figure.) That should be enough to get you in the right area of the menu, if it’s not quite right. (I’m away from my own computer right now.)