kpyip, since you have that Night Portrait function, I would recommend that you use this as a learning tool before going manual setting.
Night Portrait function usually use higher ISO to capture background lights while built-in flash helps to 'light-up' your object. At this function, expect the shutter speed to be slowed down & you might need a monopod or tripod or IS on your lens.
If you have a blur object than the background, then your focusing could be on your background instead of on your object. If the blur is caused by camera movement then object & background would both be blur. Hope this helps.
Blurred subject with OK to sharp background are usually caused by moving subject. To rectify, use higher shutter speed like >1/80. But when you do this, you will need to up the ISO to help bring the background lights in. The built-in flash or attached flash should help light-up the subject properly IF the flash unit is properly sync with the camera body thru ETTL.
If flash is not strong enough to freeze motion, your subject may turn out blur. You may also want to try M mode. Either way, I recommend getting a flash gun. Get a small one to start off, and get a cap diffuser (something like stofen omnibounce).