To create a database mirroring endpoint

To identify the ports currently being used by TCP endpoints on the
system, use the following Transact-SQL statement:

SELECT name, port FROM sys.tcp_endpoints

To use Transact-SQL to create an endpoint to use with 
Windows Authentication, use a CREATE ENDPOINT statement. 
The statement takes the following general form:

CREATE ENDPOINT endpointName

  STATE=STARTED

  AS TCP ( LISTENER_PORT = listenerPortList )

  FOR DATABASE_MIRRORING

  (

  [ AUTHENTICATION = WINDOWS [authorizationMethod]
  ]

  [ [,] ENCRYPTION = REQUIRED
       [ ALGORITHM { algorithm } ]
  ]
    [,] ROLE = role
   )