Unity is a very strange tool from .NET user's view. It's for Unity doesn't provide the NuGet package manager as a first-party tool. Unity users should work with a third-party NuGet package manager. So, if you need it setup to your unity project.
The procedure for installing NuGet Package Manager to Unity is as follows.
- Access https://github.com/GlitchEnzo/NuGetForUnity
- Download binary in release page
- Drag and drop to your Unity project
- Restart your Unity project
If you like command line, try this example shell script. It's without handling error.
Result is here.
Finally, i hope that the NuGet package manager will be standard equipment on Unity.