Here is the equipment you'll need:

ADAT
2 optical cables
ADAT sync cable
Audio hardware with ADAT optical connections (in and out) and ADAT sync in port
ASIO 2.0 drivers for the audio hardware
The physical connections
1. Connect the optical cables from the ADAT's optical In and Out to the Audio hardware's optical In and Out. (Make sure not to connect the In to the In or the Out to the Out.)

2. Connect the ADAT sync cable to the ADAT sync In on your audio hardware.

The necessary external connections should now be in place.

Setting It Up

In the audio hardware's control panel, set the clock source to ADAT (if applicable)

In Cubase/Nuendo go to Transport>Sync Setup and set the Timecode Source to ASIO Audio Device. Close this window and then click on Transport>Sync Online to prepare Cubase/Nuendo for slaving to external sync.

Now create 8 mono (or 4 stereo) audio tracks, set to a different optical input from your audio hardware and then set all the tracks to record enable. In the project windows, set your left locator where you wish the recording to begin. Set it to a point about 5 seconds before the audio on your ADAT is first heard. If you want the recording to stop at a specific point, set the right locator to that location point.

Making the transfer

Rewind the ADAT tape, press "I" in Cubase/Nuendo to activate automatic punch in and press play on the ADAT. The ADAT should start playing. Cubase/Nuendo should also start, and 5 seconds before the audio is heard from the ADAT, Cubase/Nuendo should automatically start recording.

When the song (or songs) are finished playing, press stop on the ADAT and (if necessary) press stop on Cubase/Nuendo. You will have now completed a sample-accurate transfer of ADAT audio into Cubase/Nuendo.

Keep in mind to make sure all the Sample rates match and that you deactivate record enable after the recordings are done so that you can hear the new recordings.