Question: I had a text conversation going with a friend and wanted to add another friend, but couldn't figure out how to do it. Is there a way to turn an existing iPhone message into a group chat?
Answer: Unfortunately you can only add another contact to an existing conversation if it's already a group message. You can't add someone to an existing conversation.
To create a group message, tap the "+" button at the top right of your iPhone to add multiple contacts. You can keep adding additional contacts at any time, but it has to start out as a group conversation (with 2 or more contacts from the start).