C# authentication

I think I may have missed something here. Trying to authorize so I can test other API calls. I seem to have to supply a login and password to authorize but I would think the ID and Secret would be enough. What step did I miss here? I'm using the RingCentral NuGet package inside a windows form application for now. End result would be services or console jobs that would automate things.

this is my test code:

string RINGCENTRAL_CLIENTID = RINGCENTRAL_CLIENT_ID;

string RINGCENTRAL_CLIENTSECRET = RINGCENTRAL_CLIENT_SECRET;

string RINGCENTRAL_USERNAME = "USERNAME";

string RINGCENTRAL_PASSWORD = "PASSWORD";

string RINGCENTRAL_EXTENSION = "101";

bool RINGCENTRAL_PRODUCTION = false;

RestClient restClient;

restClient = new RestClient(RINGCENTRAL_CLIENTID, RINGCENTRAL_CLIENTSECRET, RINGCENTRAL_PRODUCTION);

Task.Run(async () => await restClient.Authorize(RINGCENTRAL_USERNAME, RINGCENTRAL_EXTENSION, RINGCENTRAL_PASSWORD)).Wait();