How to configure an instance to listen on port 1433 to allow remote connection Trying to connect using SQL Server Management Studio 2012 on a Windows 8.1 Client computer from outside the cluster's domain.

Cluster is a two node Virtual Cluster made from Windows Server 2012 R2.

We can connect to the cluster from within the cluster's domain by using the Failover Cluster Virtual Network Name Account with SSMS running on another Virtual Computer from within the cluster's domain.

We have created a new Inbound Rule with port 1433 on each of the two nodes - but still don't understand how to connect to the SQL Instance from outside the domain.
If you are connecting from outside the domain you can either

1) Use SQL authentication to login.  If you have enabled mixed mode during the install you will have an sa account and you can create a sql login for yourself

2) There are other tricks, such as enabling named pipes and then authenticating against the IPC$ share with your domain account and then you can login using np:ipaddress in SSMS.  But beware it is a bit slow and most people don't want named pipes enabled on a production system.

But if you are connecting from outside the domain the easiest way is use SQL authentication.