To make Rally the primary audio device:
Windows: Go to Control Panel > Sound. Select Logi Rally as the default communication device for playback and recording.
Mac OS X: Go to System Preferences > Sound. Select Logi Rally as the default device for sound input and output.
In your video/audio calling application, check the audio settings and make sure that Logi Rally is selected for both the speaker and microphone. Then, check the video settings and verify that Logi Rally is selected for the camera.