You can save frequently sent messages in your dashboard by using the "Add template" option.
The template has been added. Now to use a saved template, just click inside the message box, add select the required template from the list visible at the right-hand side of the screen.
To remove the template from your list, all you need to do is to click at the message box to check your saved templates. Now, click on the "delete" icon to delete the selected template.