To send a text message

On the Messaging screen, tap the New message icon at the top right corner of the screen.
Enter a mobile phone number in the To field.

As you enter the mobile phone number, matching contacts appear. You can tap a suggested recipient or continue entering the phone number.

NOTE
Instead of a phone number, you can enter a name. As you enter characters, matching Contact entries are displayed for you to select.
Tap the text field to start entering your message.
1. Character counter
  
  Displays number of characters entered and amount remaining.
A counter is displayed in the top right corner of the text field to tell you how many characters are left and the number of pages.
1. Attachment Icon
  
  Tap here to attach files.
If you tap the Back Key while composing a message, it’s saved as a draft. Tap the message to resume composing it.
Tap Send to send the message.

Your message is displayed and responses appear in the same window, creating a message thread with that contact.