By supplying your SPOTIFY_CLIENT_ID and SPOTIFY_CLIENT_SECRET, you get an access token.

To request an access token, build a ClientCredentialsRequest and send it via OAuthClient. This access token will expire after some time and you need to repeat the process.

public static async Task Main()
{
  var config = SpotifyClientConfig.CreateDefault();

  var request = new ClientCredentialsRequest("CLIENT_ID", "CLIENT_SECRET");
  var response = await new OAuthClient(config).RequestToken(request);

  var spotify = new SpotifyClient(config.WithToken(response.AccessToken));
}

You can also use CredentialsAuthenticator, which will make sure the Spotify instance will always have an up-to-date access token by automatically refreshing the token on demand.