They need a hide to hibernate in, not so warm as to bring them out.
They still need some fresh water available, they sometime come out on their own for a bite of food, a sip of water, then back to sleep. Depending on species, their habitat should be maintained stable and for their natural habitat.
My desert tortoise had a small penned off corner of the garage, so protected from harsh winter weather, left undisturbed and no heating save for below freezing.
Care sheets for types of tortoise should cover hibernation and their needs.