basically solder some holes in the tub, start off with one row on both sides about an inch apart.
i actually have 2 uth's in Darth's tub because the room that he's in is kind of cold. plug your uth in to a thermostat. place the thermostat's probe in the tub. mine is under the substrate - which is newspaper.
place 2 identical hides in the tub on either side.
place your digital thermometer on the cool side with its probe on the warm side.
place your water dish (get a sturdy one) on the cooler side.
put the lid on the tub and monitor the temps and humidity. if the humidity is too high, solder some more holes in the tub.
The only addition I would make to this is check and doublecheck the tub lid. Anything more than a 1/8" give is going to let the snake escape at some point. Adding things like large binder clips, bungee cord/tight straps of some sort, even weights on the top of the lid will keep it firmly in place.