Hi,
I don't know much about Eurorack.
But i think the preenfm2 eurorack CV in are quite standard :
. CV1 / gate : triggers a new note
. CV2 / VOct : Vote per octavle. That can be callibrated in the Settings.
. CV3 and CV4 : are any CV in modulator that can be used as source in the matrix modulation.
Make sure you have a CV enabled firmare.
You should have "_cv" sufix in the title when booting it up.
And CV1-4 in the first matrix sources.