To use the Messaging features, you must set it as the default messaging app.
You can view your messages in the Messaging app without setting it as your default app, but you can't create a message.
Tap the New message icon to start a new text or multimedia message.
Tap here to create a new message.
Tap an existing message thread to open it.
Tap the Menu icon to access Search, Delete, and Settings.
Pinch in (or spread apart) on your list of messages to resize it for easier viewing or navigation.