You don't even need a page for your plugin settings, you just need a panel that only admins can see! Use the elgg_is_admin_logged_in() function and bam you're done. Well there's more custom coding involved but that should get you started :)
Take a look at my plugin to get you started on the fast track: https://community.elgg.org/plugins/2085423
Icon on the bottom right is only available to admins. BTW, documentations are always a BIG help: http://learn.elgg.org/en/1.11/guides/settings.html
info@elgg.org
Security issues should be reported to security@elgg.org!
©2014 the Elgg Foundation
Elgg is a registered trademark of Thematic Networks.
Cover image by RaĆ¼l Utrera is used under Creative Commons license.
Icons by Flaticon and FontAwesome.