To add data to the form at user-new-php
, I believe you want the user_new_form
hook. Unfortunately, it is marked “@since 3.7.0” so it isn’t in the stable release yet.
I am tempted to tell you to hack it into your site in exactly the place that it will soon appear, but that would be wrong. 🙂 You will have to wait, or install the subversion release.