Photo editing is a huge topic to cover, certainly in a written format like this. With nightscape photography, there is no getting away from the fact that over 50% of the work involved in a successful image is in the editing.
The advice I would give is to spend some time on YouTube, where there are myriad different tutorials on how best to edit your nightscapes that are also specific to the editing software you have installed on your computer. I would recommend watching different channels and decide which approach is right for you, your images and your editing software.
Always shoot your nightscape with the end result in mind. When you set up your tripod and frame the composition, ask yourself why you are attracted to this view. What do you want to achieve with the result? How are you going to manage noise in your image, or how are you going to avoid noise in your image? How light do you want your foreground to be, and is this going to cause any problems when it comes to exposure blending if shooting multiple images?
Depending upon your editing software, I would recommend making sure you know how to work with the following:
- RAW image editing (all your nightscapes must be shot in the RAW format for maximum detail capture)
- focus stacking
- Layers and Layer Masks
- Making Selections and editing those specific selections
- Adjustments
- Blending Modes
- Image stacking
As you become more of an advanced user, you will pick up other tips and techniques along the way to personalise your workflow and make the process simpler for you.