Je suis né(e) à Lewisham.
* Je suis né(e) means "I was born" and changes depending on your gender (né for male, née for female).
* à means "in" or "at" and is used before a location.
* Lewisham is the name of the place.
You can also say:
* J'ai vu le jour à Lewisham. (This literally means "I saw the light of day in Lewisham" and is a slightly more poetic way to say it.)
* Je suis originaire de Lewisham. (This means "I am from Lewisham" and emphasizes your origins rather than your birthplace.)
The choice of phrase depends on the context and the nuance you want to convey.