I don't know about macs, but search for 'Nebula Server' and make a shortcut (alias?) to your desktop then double click the icon which activates the server. Do that before launching your host/sequencer.
When you launch Nebula in your host, click the 'Disk' page where you should see something like 'Server 6000'.
'Hope that helps,
Cubase 9 Pro x64 + jBridge, W10 x64 Dual Boot on 2 SSDs + 3 SSDs for samples & project files, i7 5930K @ 4.2GHz, ASUS X99 Pro, 32GB RAM, RME HDSPe AIO, 2 x UAD2 Solo, Mackie HR624 MK2, 2 x 24" BenQ LED monitors, Nebula 3 Pro & Server x64.
I take that back. My RAM issues are the result of using too many instances of Nebula, even with the consolidation taking place. Tested with and without server, dedicated and separate processes, definitely save using Server or a single separate process. Problem is that CPU is pegged at 99% with server and the system skips, back to dedicated processes within Reaper.