Syntorial is a standalone application, designed to run on its own, not in a DAW. After installation you'll find it in:
Windows: "Program Files (x86)\Syntorial"
However, the synth used in Syntorial is available as a VST plugin, that IS meant to be used in a DAW. It's known as Primer, and it's available for customers who have purchased the full version of Syntorial. To get Primer:
- Log in at syntorial.com/account
- Select "Downloads"
- Download Primer