The iZotope Stutter Edit works differently than other audio effect plug-ins, it requires MIDI input from your host to trigger its effects. Not all hosts allow you to send MIDI to audio effects.
Fully Supported Hosts:
Depending on the host application, there are different ways to use Stutter Edit on Audio and on Software Instruments. Please see links below for some short video tutorials on how to inset and use Stutter Edit in different host applications:
For a paper walkthrough on all supported host application, please see the iZotope Stutter Edit online manual, linked here.
Once the manual is loaded please expand the Quick Start header in the left hand menu and choose the host application you are using.