This tutorial will step you through how to add a custom UI for your plugin.
In your plugin class, you need to create a new class that inherits from IPluginMenuItem.
This should return a string which contains the text the user will see when accessing your plugin menu from the InControl UI.
This should return a list of PluginSubMenuItems which will be displayed to the user from the UI. You can return as many menu items as needed in this list. Each menu item will have a menu name and should specify an onMenuItemClicked event which runs when the user selects the menu.
To create the actual UI that the user will see, you should add a new XAML file to your project. Name it PluginSetup.xaml
Proceed to add the appropriate controls to your xaml markup. For details on how to create controls, please refer to Microsoft WPF.
Create a 2nd page (if it doesn't already exist), called PluginSetup.xaml.cs.
Continue to implement your UI's logic in this class.