Click “Manage Navigation” from the Home page.
Select “Add Sub-Menu Group...”
Complete indicated text fields in the pop-up box and click "Add Sub-Menu Group"
The sub-menu group is now created within your web page.
Click & drag the sub-menu group to the right-most "Web Site Navigation" column in your desired order
Click the carrot icon on the side of your sub-menu group to view its contents.
Drag & drop web pages from left-most column to right-most column to add them to your navigation.
Click "File" then "Save Menu". You may need to clear your cache if your changes aren't "sticking".
You'll now be able to view the sub-menu on your site.