Are you using Apple iPhone or just a normal phone?
Well, it doesn’t matter actually. You can configure to send/receive MMS on any phone as long as you get it right.
Quoted from their website:
This service allows you to view multimedia messages (MMS) that have been sent to you. For every message you receive, you can reply with your own multimedia message, or forward it to someone else.
Multimedia Messages can be sent by people with camera-equipped mobile phones and may contain pictures, sounds or even video clips. If your handset cannot display the contents of the message, it is sent here where you will be able to view it.
For a complete review and setting; please refer to: