JSoft

Not sure if you still need help with this but Redshift/RoyalRender user here for the past 6 years or so. Setting this up is a bit confusing but you're on the right track.

In your local preferences folder (c:\Users\you\AppData\Roaming\MAXON\Cinema_Version) you'll find a settings.userinstallation.json file. This stores the path of the shared asset database that you set up to use locally.
 
The next step is to copy that .json file to a shared location and edit the Royal Render environment to use that shared prefs location. The RR docs explain how to edit your environment variables but again it can be a little confusing with all of the files involved.
 
In the RR install folder the environment files are in //RoyalRender/render_apps/_setenv/all. There is an environment config for each 3D app so look for the cinema 4d*.rrEnv ones. Note that the only one you should create/edit is the cinema 4d__inhouse.rrenv file. This is your custom environment that remains untouched by any RR updates. Add the g_userprefs = Z:\PATH_TO_SHARED_PREFS line to this file. All Royal Render clients will now use that shared prefs directory and the corresponding asset database(s) that are defined in the .json file.