If you don't see a bell icon in *any* of your ticket-types, then you do not have the license for the notification feature... Notification technology is part of the "workflow automation" module ; this is the typical BackStage module that brings ticket-chaining, hotfolders, notifications and lots of other automation stuff. This can be seen in their 'guide to BackStage modules' that is posted on their website
BackStage - Esko (see below-right on that page -see 'more information'. Zoom into the modules to see their contents)