You can send iMessages to phone numbers or email addresses if the recipient has a device that supports iMessage. Before you can send and receive iMessages, you need to set up your mobile phone for iMessaging.
Tap the new message icon.
Tap To and key in the first letters of the recipient's name.
Tap the required contact.
If the recipient can receive iMessages, iMessage is displayed in the text input field.
Tap the text input field and write the text for your iMessage.