BEFORE EDITING

As you can see, the image is very dark, but that's something I wanted, as I was shooting in RAW format, so I get as much information about the night sky and the aurora as possible.

AFTER EDITING

To bring out the colors more, I used 2 adjustment layers, Exposure Adjustment and Brightness & Contrast. I also used a Mask for the reflections on the water, but was very careful with this one to not over expose the section. 

(I also used the Inpainting Brush Tool to get rid of the posts and the lights in the background. Also, I put a filter on top, using Noise -> Denoise, to get rid of any noise in the sky).