Notifiers can be set by typing in a name in the field under it and selecting from the selection the auto-search generates. Additionally, you can notify users if the form gets submitted, approved, forwarded, rejected, or if the form expires by checking the corresponding checkboxes:

A box showing you the names you have selected and about what they will be notified will appear like below after you press :

If you decide to delete a permission or rule, you can simply click the red bin