To send a reply, choose the desired link from the Negotiate > Reply to a Request menu.

Enter the text of your reply in the text box and click the corresponding Send/Add button to insert the message or note.

Note:  the Add Message option will be visible to both parties' Activity Log and will put a Message icon on the opposing party's Work List.  The Add Internal Note option will not be visible on the opposing party's Activity Log.

When the message is saved it will then display in the Activity Log. Choose the Less Detail option to focus primarily on messages and notes.