PhotoScapeX can be used accurately with 3 or 4 clicks or you can REALLY get into serious editing. Here are a couple of sites for you, Enjoy. Be sure to select Mac/or Windows. Get the free version first (it never expires), and you can always upgrade. Also, please do yourself a favor and watch the following YouTube videos to see if you would be interested and for training. https://www.youtube.com/watch?v=nWC-SAuYOzw&t=325s Instruction and download info http://x.photoscape.org/

Smile,
JimmyT Sends

Lots of good advice already mentioned above, but I think Gene's suggestion of this, "Even if you are shooting at night, there is always a way to get natural looking and flattering light from a flash - even if it means you need to bring a friend to hold a large bounce surface so that the light source is large and nicely diffused, yet directional." is an excellent idea. And if you can get say a piece of white poster board, maybe at least 2 feet by 3 feet, or piece 2 together for a larger reflector it would be ideal. You also would need an assistant to hold it.
Direct flash is a very hard light, very harsh, and very unflattering. The goal is to make that small light source larger by bouncing it off a larger surface. If you can do this you might want to start with the following setup:
1) swivel the flash around so the light is aimed over your right shoulder, and have your assistant standing back there with the white poster board aimed at the flash. That person should be no further away from the flash than 3-4 feet.
2) I would shoot in full manual and start with a setting of f/5.6, and a shutter speed of !/80 -1/100. This is slow enough to pull in some ambient light (of the Christmas lights) but not too slow to create the possible problem of motion blur that still can occur when using flash with too slow a shutter setting.
3) Set flash to full power, do a quick test shot and see how the exposure looks by checking the histogram. If you think it's too overexposed you can incrementally correct that 3 ways. 1) reduce the flash power output, 2) move the poster board a little further away from the flash, or 3) close your aperture down some, maybe to f/6.3 or f/7.1. My typical choice in a situation like this would be number 3, start by closing down your aperture. But, any one of those, or a combination of those will help.
A little tidbit about using flash or lights: your shutter speed controls the amount of ambient light entering the camera, and your f/stop controls the amount of flash entering the camera. And you can start with your camera's native ISO, maybe ISO 100 on your camera, but an ISO setting of 200 should also be fine. Lastly, disregard what the meter is showing you with the settings I mentioned above and with the camera in full manual mode...it will indicate that you are grossly underexposing the shot, but the flash if used properly will provide for that.