From the Home screen, tap Google folder > Hangouts .
Tap the New icon (at the bottom-right corner of the screen) > NEW CONVERSATION.
Tap the name of the person in your contacts list. If your friend is not yet on Hangouts, your friend will receive an SMS inviting them to Hangouts.
OR
Tap the text field to enter a name, email, number, or circle.
Tap the message box (at the bottom of the screen), then enter your message.
Before you enter the text for your message, you can tap the Attach icon (to the right of the message) to attach a photo, video, or location.
Tap the Send Icon (on the right side of the message).
You can tap the call icon (at the top of the screen) to call the friend, or tap the video icon to start a video chat with your friend.