Explain Everything features more than one way to guide you through the app. There's the help file, a dedicated iBook showing all the functions of the app and pop up windows that show up whenever you access a new function for the first time. There are online video tutorials showing how to work with the app.
Download Explain Everything™ for iOS: itunes.apple.com/app/explain-everything/id431493086
Explain Everything™ website: explaineverything.com