To continue an existing conversation, tap its link on the Home screen.
In an existing conversation, you can:
Send a new message or photo.
Use predefined message text to send a message quickly.
Add participants to a conversation.
New Messages and the Conversation Log
If you are returning to a conversation and new messages have been added to it, the new messages are clearly marked in the conversation log.
Sending a Message
You can send a message to a conversation or group chat that you are in.
Adding a Participant to a Conversation
If you are in an existing group chat, you can add another participant to it. If you are in a conversation with one other person, and you want to add a participant, you can create a new group chat consisting of you, the other person in the conversation, and the new participant.