Step::1 Login to WHMCS admin panel.
Step::2 Go to ‘Support’.
Step::3 Click the option ‘Predefined Replies’.
Step::4 Click on the tab ‘Add Category’.
Step::5 Enter the Category name and click the button ‘Add Category’.
Step::6 Click on the newly created category & then click on the tab ‘Add Predefined Reply’.
Step::8 Type the ‘Article Name’ and click ‘Add Article’.
Step::9 Enter the pre-defined reply and ‘Save Changes’.
That's It !Go through the video tutorial to get the explanation in detail. You may check out the blog as well.