How do I access the Node Access User Reference configuration? I've installed the References and Node Access User Reference modules on my Drupal 7 system.  I've added a User Reference field to a content type, and can happily add user references to nodes.

However, on the Node Access User Reference's project page, it shows a screenshot of a configuration form which I cannot find.  I want to grant referenced users editing rights, but cannot find where to do this.  Where do I find this form?
I found a clue in the README.txt which I'd previously missed


  Create a field to reference users in a content type using the Field UI.  The field's
  configuration page will contain the settings for Node access user reference.


I edited the User Reference field I'd created, and on the Edit tab was a collapsed heading for Node access user reference that I'd previously missed.  Clicking the heading revealed the configuration form.