Subtable Problems

I have a membership parent form and want to show a subform that shows all of the members the parent member has recruited (referred). I’ve tried creating Multiple Versions but cannot link records from the same source. I know this is fundamentally basic stuff, I’ve done parent/child forms in other languages a thousand times, but for some reason I cannot wrap my head around this. I am trying to link Parent.ReferredbyName to child.FullName. I will continue to work on this. TIA!

Please refer to the following manual