Currently, Arpado is a stand alone application. It's not a VST plugin. We are currently working on developing a VST Bridge that will ease its integration on any VST Host, including most famous DAWs out there.
However, there are ways you can make it work right now within your DAW:
Record audio output from the instruments that play the notes sent by Arpado
Use the Record feature in Arpado to capture your performance and export it to a MIDI file, which can be imported in the DAW