one cannot delete a user, as such, but can make them innactive - admin->users then choose the user you’d like to mark as innactive - a check box near top right hand of the form
patients can be deleted from the dashboard by a user who has permission to delete patients
to make a user innactive click on their name in the list you showed us (admin->users), this brings up configuration for the chosen user in which you’ll find the active/innactive button