E M-5 and flash

Hi. (the flash am using is the little one that came with the camera)

Taking a portrait with the face relatively dark while the background is bright, the camera will set the exposure to the background, and does not trigger the flash. So the background will come fine but the face comes dark.

Instead, if the camera sets the exposure to the face, then the background will be overexposed.

I would like the camera to set the exposure to the background, and lallow me to "force" a little flash to fill in on the face.

Cannot find in the menu how to do that. Could someone please explain? Thanks.