Q. Do I have to practice witchcraft naked?
A. No, you don't have to. Some witches do and some don't. The term we use is "skyclad", and it's not a universal practice among witches or Wiccans. Some Wiccans who are solitary go unclothed when doing rituals, and covens may also do the same. But that doesn't make us nudists. It is not a requirement that you be naked during rituals or any other gatherings just because you are Wiccan. It may be a requirement of a particular coven, though.
There are several reasons why nudity might be desired during rituals:
Nudity is usually restricted to formal rituals, rather than being a part of a witch's everyday life.