Yay, welcome to the world of speed flash photography. You should start reading http://strobist.blogspot.com
To get you started, here are some simple camera setting to improve your night shot.
- Switch your camera to Av mode
- Keep Evaluative Metering mode
- Set your camera to the faster aperture as possible and still maintain the good DOF. Eg: f2.8 on 50mm lens.
Without flash, fire it. Note that the scene is correctly exposed but the subject could be underexposed if it's backlight. That's why you need to add fill flash.
Attach and turn on the flash, change the flash's mode to E-TTL
(extremely important), and without changing any previous setting
, fire the shot again.
Now, your subject should be lit properly and the background still maintain a good exposure, not DARKEN.