»Click here to display Table of Contents« User Security > Working with Users:
To delete a user from the list, either click on the user name and then choose Delete, or, from the main user list, click on the delete icon on the far right. When prompted, confirm that you wish to delete the user. The user is removed from the list.
Help URL: http://www.yourdomain.com/help/index.html?usersecurity_deleteuser.htm