Launch Logic and open your current project (File/Open Recent).
Then go to Audio/Audio Mixer and insert ARC as the last plug-in in the Out 1-2 track. If you have to create an Audio object, go to Windows/Environment/New/Audio Object.
In the Audio Object’s parameter box, set the Channel parameter to the desired Logic Audio Outputs (e.g., output stereo 1-2).
Now, insert ARC Plug-In on the newly created Audio Object.