Login to your hosted chat management interface at https://<your_link>.hosted.chat
Click “More" and scroll to "Canned Messages" Screenshot: https://www.screencast.com/t/tVKyRmGk
Click on the plus "+" button to add a new Canned reply
Just fill in the "Title" (what your agents will see) and "Message" (what your clients will see) fields, and click "Save".
Now your agents will have the canned reply available when responding to a client