First time using a substack

[RossG]

I've added a card/substack (not sure what it's called)
but can't find a way of putting info. into a field on it.

How do I put "2" into field bz16 of stack "Results"?

Update: The answer is as the line above but due
so a slight error in a field name (Where have I
heard that before?) it didn't operate as expected
although the error message was clear enough.