This guide will walk you through the steps to insert a text message within your chat stories.
Navigate to the story where you want to insert a message
Tap the Pencil icon at the bottom right of the messages to enter edit mode.
The pencil button becomes an X, and editing options appear.

Tap the + icon at the position you wish to insert the message
Select Message from the Insert menu that appears.
Select the Character who's sending the message
Choose between Text or Photo or video message
For a text message, type your desired message content into the text field.
Press the Send button to the right of the text field to add the message to the chat.
This article explains how to insert text messages in your TextingStory creation by using the edit mode.