Referred by column is empty

We're testing the Affiliates plugin, and it's working, except for...

In wp-admin -> users, there is a column called 'Referred by'.
But that column is not populated.

I see some functions for that in affiliateadmin.php.
Is there something else that we need to do to populate that column?

Also - is there anyway to see that info somewhere in
wp-admin/ Affiliate System Administration ?

Ideally, we'd like to see all users that were referred by a certain user.
And be able to see who a user was 'Referred by'.

Thanks.