When you create FlippingBook HTML Publication, the software generates a publication folder which contains an index.html file, .htacces file and "files" folder, as in this screenshot.
First please upload the publication folder to your server. To embed the publication, you'll need that folder URL.
The other thing you need is WordPress iframe plugin. Please download it from http://wordpress.org/plugins/iframe/ and install it to your website.
After that creating an iframe is quite easy. Just use the publication URL as the iframe target, as in this example:
[iframe frameborder="0" width="640" height="480" title="Example" src="http://your-web-adress.com/publications/Publication_name/" type="text/html" scrolling="no" marginwidth="0" marginheight="0"]