It means "to live" or "to reside."
Here are some examples of how it's used:
* "He dwelleth in a fair castle." (He lives in a beautiful castle.)
* "The dragon dwelleth in a cave." (The dragon lives in a cave.)
* "She dwelleth in the forest." (She lives in the forest.)
While "dwelleth" is a bit archaic in modern English, it is still sometimes used in literary contexts or when trying to evoke a sense of old-fashioned speech.