There are a few options. the easiest, go to media, then pictures and find the picture you wish to send. highlight it, press the menu button and then send MMS.
You can also go to messages, then menu compose MMS, then add address then scroll to body of message and hit menu then add picture and select the file this way.
Remember that it is a good idea to check and see how many MMS messages you can send with your current plan before you are charged. MMS is different than SMS so they should be listed separately.
