A long time ago in a galaxy far, far away, we used to configure NuGet package sources at the machine level in Visual Studio. Each time a new PC was dropped on our desk, we would dutifully go through our Visual Studio configuration steps, including setting up a NuGet package source pointing to our ProGet server.
Recently we have been able to reduce the amount of configuration needed at the machine level by instead configuring our package source at the repository level.
The packages source configuration is in a nuget.config that gets committed to the repo right beside the .sln.
You can learn more about nuget.config from the Microsoft Docs.