Yes. When using ADAT, using a Wordclock cable is always a good idea.
WC Cable from the 1818 to the DigiMax 96K
ADAT OUT of DigiMax 96K to ADAT IN on 1818VSL.
Set the DigiMax 96K to sync to WC
Now in your DAW make sure you add the additional input channels to your I/O setup to make sure you can route those inputs into your system.