To open Messaging
From the Home screen, tap Messaging
.The Messaging screen will open, where you can create a new message or open an ongoing message thread.
New Message Icon
Tap here to create a new message.
Tap the New message icon
to start a new text or multimedia message.Tap an existing message thread to open it.
TIPQUICK REPLY
When a New Message notification is displayed, you can reply quickly without accessing the Messaging application. Simply tap the Text field in the notification to respond with a text message, or tap the Call icon
to call the person instead of responding by text, tap View to
open the Messaging application, or tap the Delete icon 
to delete the message.