What do you mean with “setting page”? A screen with configurable options in the system console of the mattermost server the plugin is running at or a screen that pops up when you type a command or click on some GUI element?
You should be able to find both things in the code of the badges plugin, f.ex., since it opens dialogs on slash commands, has a custom plugin setting page and also an entry in the appbar on the right to show the available badges.