To send a message from the desktop/WebRTC app first click on the magnifying glass icon.
Then enter the extension number or telephone number of the party that you want to message. Click on the text that says “Create a conversation” and you will be able to enter your text message.
If you have a Contact that matches the number, it will be displayed. If you do not have a matching contact, then a new local contact will be created. One the contact is displayed and selected, click the Enter button to compose a message. The resulting page will show your communications stream with this contact.