In their clothes, in a toiletless cubicle in the toilets.

... In their clothes, in an empty cubicle.

So some of the cubicles in the toilets will have a toilet in it for pooping, and other cubicles without them, for wetting your pants in. If you only need to pee, you are expected to go into the empty cubicles and wet. The toilets will not be designed for you to pee in them, and if you get pee on the floor in those cubicles you will be in trouble, so it would be best to pee in the empty cubicles if you need to go. As for at home, you just wet yourself in your bathroom.

You may be wondering, why can't you just pull your pants down to pee. Well, in this world it is seen as perverse to get naked for any reason other than changing, pooping and cleaning oneself. If they catch you in dry pants, they may give you funny looks. You are even expected to wet yourself before you leave the house. In fact, if they know you intentionally pee outside of your pants that would be seen as immodest."