How to include userid, pass to WifiClient connect() api

These are my remote server credentials that I want to connect from my local device.

Server  m12.cloudserver.com
User    <myname>
Password    <mypassword>
Port    19999
_ or 
api_key 5678909876-009-00d

I want to use the WiFiClient client() API as shown, but where or how do I include the User credentials ? so that I can make a successful connection to the remote server from my device connected over Wifi.

Cut and paste from my Arduino code.

const int httpPort = 19999;
if (!client.connect("m12.cloudserver.com", httpPort)) {
 Serial.println("connection failed");
 return;
}