To use external plugins, you must manually point the software to your VST folder: How to Autotune with Adobe Audition - 2 Minute TUTORIAL
Adobe Audition 1.5 and that specific VST version were a rite of passage. They represented the bridge between the analog mindset and the digital future. It wasn't about being "fake"; it was about the magic of a piece of software making a kid in a bedroom sound like he belonged on the radio. Autotune Vst For Adobe Audition 1.5