Plug one end of an audio cable into one of the "Output" jacks on your audio interface, and plug the other end into one of the "Input" jacks on the ADAT recorder.
Repeat Step 1 for each audio channel you need to route into the recorder. For example, if you are recording a stereo mixdown, two channels of sound (right and left) is sufficient. You can connect up to eight channels using up to eight TRS cables, or route up to eight channels through a single optical audio cable.
Turn on your computer, and click the desktop icon for Cubase to launch it. Click "Start," then "All Programs," and select Cubase from the program list.
Click "Devices," then "Device Setup" and select your audio interface if it is not already selected.
Click "Devices," then "VST Connections" to open the "VST Connections" window.
Click the "Outputs" tab, then click "Add Bus." Click the "Configuration" drop-down menu and select the configuration that corresponds with the number of outputs you have connected.
Right-click the "Output" displays on each track to be sent to the recorder, and select the output bus for each track you want to send to the recorder. You should see a response on the ADAT's level meters when you're playing any of the tracks routed to it from Cubase at this point.