Step 1 Press Insert + F6 to get a list of headers and search for Write a comment: 6 header. Then press Enter on it to select it and press Enter again to get the prompt to type a comment. 

Step 2 Type your comment.

Step 3 To save, press Insert + F5 to get a list of form fields. Search for Save Button and press Enter to select it and press Enter again to save the comment. Alternatively you can press Control + S to save the comment.

Step 4 To cancel, press Insert + F5 to get a list of form fields. Search for Cancel Button and press Enter to select it and press Enter again to cancel and exit the comment prompt.