How high do the stats need to be? And do you need the latest patch for it to work?
If you use the version which is linked here here (which by now is technically outdated, even if it contains more modded clothing and stuff)
and have the patch applied that is linked below the DL, it should show the options not too long after being able to modify the girls wardrobe. I definitely remember you don't need to max them out for the option to appear though. Applying the patch does not just fix a bunch of bugs - one of which I remember being a critical bug in some menu - but also added 1-2 more outfits for some of the girls.
From what I remember. it's as simple as selecting a girl, talk about her clothing, select a clothing category (as in tops etc.) and you should either have more clothing pieces listed, or a subcategory named "modded wardrobe" appear in that menu. Though from what I also remember, the games' interface is cluttered as fuck and for some characters, you can actually scroll through clothing options simply because it's too many to list them the way the game handles that normally.
However, it's been a while since I have played the version that is linked here specifically, so I'll do a re-run to make sure I'm getting all of that correct.