Just install the package using the Package Manager inside Visual Studio or via the console.
dotnet add package NewsletterStudio
We host several packages on NuGet:
NewsletterStudio - Contains only UI-file (App_Plugins)
NewsletterStudio.Web - Contains Umbraco-dependencies, most of the time any custom class library you might have should depend on this package.
NewsletterStudio.Core - Core files for the package with minimum external dependencies. Reference this package when you want to extend the functionality.
NewsletterStudio.CssInline - Package that deals with inlining css into html when rendering the email.
