Adding app help (HTML)
Add a help section to explain to users how your app works. To incorporate help in your app, take advantage of the Settings charm by adding a "Help" command to the system-provided Settings pane and placing your help content in a Settings flyout.
All Windows Store apps automatically participate in the Settings contract. Even if you never modify your app's settings, a user will be able to click on the Settings charm from within your app and see a default Settings pane. This pane is always 346 pixels wide and contains a list of up to seven settings commands. If a user clicks on one of these commands, the Settings flyout associated with that command replaces the Settings pane onscreen. The default, system-provided Settings pane includes a "Permissions" command and, once your app is installed, a "Rate and review" command that sends a user's feedback about your app directly to the Windows Store.
Using C#/VB/C++ and XAML? See Adding app help (Windows Store apps using C#/VB/C++ and XAML).