As always, the best way to install the package is using the NuGet command-line interface within the Visual Studio's Package Manager Console. From there, type the following:
add package Microsoft.AspNetCore.Authentication.Facebook
At the time of writing, the package's latest stable version is 2.0.0. As always, the reader is free to either stick to the recommended release or to try a newer version, as long as he can handle the upgrade.