Base url of package registry ('npm adduser --registry=http://myregistry.example.com')

var settings = 
        new NpmAddUserSettings 
        {
            Registry = "http://myregistry.example.com"
        };
    NpmAddUser(settings);

Scope assoicated with the user ('npm adduser --scope=@cake')

var settings = 
        new NpmAddUserSettings 
        {
            Scope = "@cake"
        };
    NpmAddUser(settings);

Indicates that all requests to the given registry should include authorization information ('npm adduser --registry=http://private-registry.example.com --always-auth')

var settings = 
        new NpmAddUserSettings 
        {
            AlwaysAuthenticate = true
        };
    NpmAddUser(settings);

What authentication strategy to use ('npm adduser --auth-type=legacy')

var settings = 
        new NpmAddUserSettings 
        {
            AuthType = AuthType.Legacy
        };
    NpmAddUser(settings);

Use specific log level ('npm adduser')

var settings = 
        new NpmAddUserSettings 
        {
            LogLevel = NpmLogLevel.Verbose
        };
    NpmAddUser(settings);