If you want to provide sound or text tips for pages of your books, you can enable the Assistant Feature, edit scrolling text, record audio or insert sound directly. Then readers can follow your tips, listen to the audio you applied, get more interest and info from your book.
Click "record settings" icon to enter into Record Audio interface.
Or you can click the inverted triangle icon to import an audio file directly.
In the Record Audio window, input "Audio Text" for each page, and then choose Text-to-Speech engine, and then click "Generate audio". After generating, you can click "Play audio" to listen to the audio, you can also choose "Import audio from existing file" to apply existing audio directly.
About Text-to-Speech engine install and use, you can view details in this page: http://www.flipbuilder.com/support/how-to-read-your-text-to-readers-in-flipping-book.htm
And if you want to choose more Text-to-Speech engines, you can follow this: http://www.flipbuilder.com/support/can-i-choose-more-text-to-speech-engines-to-record-and-read-the-text-in-the-flipbook.htm