The chat serves primarily for non-verbal communication. However, it can also be useful for taking notes and following the transcript of the session, as all activities and shared documents are listed there.
To send messages,
Step 1: The Chat window allows you to send text messages, as well as view the transcript of the session. (Fig. 22, Below) (8)
Step 2: To send chat messages, please enter the text in the designated field. (Fig. 25, Below) (1)
Step 3: Upon clicking on “Send” your message will be sent and will then appear in the chat history visible to all users. (2)
Step 4: You also have the possibility to upload image files to the chat (3) and share them with other users or edit them together. 
For more information on uploading image files to the session see "How can I collaborate on snapshots on Android?".
