Connect NUC Roon Rock with Mac

Hi there
I recently transported my core from my iMac to a NUC Rock Roon server (the iMac was to busy)
Now i want to let the roon rock server use 1 directory for reading for music? And i want to make (first restore) the backup on my iMac.
How can ik tell roon rock to look on my iMac directery and use my iMac for backup.

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