I am in need of help to add flash to the built in one. Maybe i need extra help with flash maybe not,but regardless my new external flash does not work, the built in one works fine.
The Strobist blog is a good place to learn about flash photography, although it's mainly manual settings (rather than TTL - an abbreviation for you to research there).
I recently started using a SB400, which is Nikon's least expensive external flash. Mostly, I swivel it upwards so it faces the ceiling and set the camera's flash setting to "rear". The only issue is that it doesn't work so well in this fashion when shooting in a portrait orientation.