Run PaleNightTheme.vsix (Visual Studio must be closed)
Run Visual Studio
Go to Tools-> options
Choose PaleNight Theme from the drop down box
Click OK.
Let me know if you find errors or want me to make some changes.
You can also customize the colors from Fonts and Colors in Visual Studio options
Or download the project from the repository to modify it in your own way and generate a new theme (Extension), for this you will need to have the Visual Studio Color Theme Designer Extension installed