I keep forgetting ASIO functions different than WDM.

Hi:
 
Make sure you select that input in the Input Drivers section in the Unified Preferences view under Audio>Devices. (To get to the Unified Preferences view, in the top left side of SONAR, go to Edit and then select Preferences.)
 
Then, it should be available in any audio track from the track's input dropdown list.

Make sure you have the ADAT inputs selected within the Fireface driver application accessed through the ASIO button within Sonars Preferences>Audio section.

I've never tried to use ADAT2 before, but I selected "All Channels" under Bandwidth in the Fireface control panel, and checked under audio preferences in X3e, X2a, X1d, and 8.5.3 (all x64, all Producer) and only the 8 stereo pairs of ADAT1 show up in any version.  That's with the latest version of the control panel (3.085, HW rev. 2.77).