FL Studio as a VST

How do I go about adding the kicks, claps, etc to seperate mixer channels on Cubase?

The FL rewire/plug in has 16 outs that can be activated like other plug ins in Cubase. This should map the FL mixer channels out to the Cubase mixer channels. Then I suppose it’s just a matter of routing your instruments in FL to the FL channels. I have FL but don’t use it much at all. But I have played around with it couple of times and have activated all 16 outputs without any issues. I’ve never done any internal routing in FL so couldn’t help you with that part. Hope this helps.