RLS and UserPrincipalName()

Hi folks,

I took my first foray into implementing RLS in a report that I published from PBI Desktop to our firm's Power BI Service environment, but it, unsurprisingly, hasn't been working. I've been studying a solution here:

https://community.powerbi.com/t5/DAX-Commands-and-Tips/Configure-Row-Level-Security-with-OR-condition/m-p/948434

Using the above thread, I setup a test RLS table with a handful of "authorized" users, which I would use as a filter in tandem with userprincipalname() to ensure only they can see this report. I used a variation of this DAX expression as a filter for each table in my report:

= CONTAINS('RLS', 'RLS'[Email Address], USERPRINCIPALNAME())

Unfortunately, it doesn't work. What should this filter being set against left of the "=" sign? If its a column like [Email Address], I get errors stating the column couldn't be found and/or is now allowed in the expression. Also, the aforementioned thread suggested that the RLS I set up doesn't need to be given a relationship to any of the tables in the model, which seems contradictory to other solutions I've read (unless I missed something). Appreciate the help in understanding this better. 

Best,

pb