Your messages can be sent as either regular SMS or iMessages. iMessages can be sent to phone numbers or e-mail addresses if the recipient has a device supporting iMessages. Remember, you need to set up your mobile phone for iMessaging.
Press the new message icon.
Press To and key in the first letters of the required contact.
Matching contacts from the address book are displayed.
Press the required contact.
If the recipient can receive iMessages, iMessage is displayed.
Press iMessage and write the text for your iMessage.