How to use basic UNIQUEID()?

[edApps]

I'm new to GAppSheet. I regret to ask this question, but after several online videos and lots of poking around, I still can't understand how one sets a particular column to the UNIQUEID() setting. I have a column named [_RECORD_ID] that I'd like to  use as an automatically generated ID value. Where and how do I do that? I've tried to set the auto value to =UNIQUEID(), but it calls that invalid. So, I'm at a loss.

Thanks