While we could just allow the player to enter IP addresses to connect to servers (and many games do, such as Minecraft), it's much more convenient to allow the player to browse a list of public servers. This is what the Master Server is for.
Now that you can start up a server and connect to it, let's take a look at how to connect to the Master Server you downloaded earlier. First, make sure both the Master Server and Facilitator are running. I will assume you are running them on your local machine (IP is 127.0.0.1), but of course you can run these on a different computer and use that machine's IP address. Keep in mind, if you want the Master Server publicly accessible, it must be installed on a machine with a public IP address (it cannot be in a private network).
Let's configure Unity to use our Master Server rather than the Unity-hosted test server. The following script configures the Master Server and Facilitator to connect to a given IP (by default 127.0.0.1):
using UnityEngine;
using System.Collections;
public class ExampleUnityNetworkingConnectToMasterServer : MonoBehaviour
{
// Assuming Master Server and Facilitator are on the same machine
public string MasterServerIP = "127.0.0.1";
void Awake()
{
// set the IP and port of the Master Server to connect to
MasterServer.ipAddress = MasterServerIP;
MasterServer.port = 23466;
// set the IP and port of the Facilitator to connect to
Network.natFacilitatorIP = MasterServerIP;
Network.natFacilitatorPort = 50005;
}
}