If you have a policy defined at the root organization level, you'll find that you cannot add notifications to it at the organization or application levels, the UI will be greyed out.
To work around this, define a new role in Nexus IQ Server that will be used for the notification. Edit the policy in the root organization, and assign notifications to the new role.
Then in the application select "access" settings and then "add a role". Choose the role you just created, and assign uses to this role.