I don't mean for my character, I mean for forcing other characters that I've knocked out and am messing with their inventory to grow one. If I go to the vagina selection there, the default is clitoris size.
Also: how do I make potions? I've got a bunch of ingredients, but no idea where to start.
You don't enchant clothing when you want to grow a vagina. You're supposed to create a potion to do any drastic transformations, and when forcing random NPCs you simply pick the potion you created and shove it down their mouth. Enchanted clothing are cheaper for size changes, but they can't transform body parts out of nowhere.
As to the making potions question, simply pick a potion or food item in your inventory, and then select 'enchant'. This brings you to the potion creation menu, with options based on the original potion. If you want to make people grow vaginas, then win, disrobe to see what genitals they have (pending on the gender options they could be cuntboys), and then find the racial food associated with them (ex: kitty's reward for cat-people), and then enchant that to have the racial vaginal transformation. If they don't have a vagina, they'll then grow one of the race that you enchanted the potion with.