There are two rules you need to follow to add notifications. First, you need to add notifications for your custom events so that emails will be sent out when they are fired. Second, you will want users that are specified in the CC list custom field to also receive emails along with the assignee and reporter of the issue:

1. Click on the Notifications link for HR Notification Scheme
2. Click on the Add notification link
3. Select the Issue Updated event type
4. Select User Custom Field Value for the notification type and select Direct Manager from the drop-down list
5. Click on the Add button

Nice and easy. With just a few clicks, you have added the Direct Manager custom field to the notification scheme. So now, regardless of who is put into the field, the user will receive notifications for issue updates.